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500 Internal Server Error after upgrading from 9.13.10 to 10

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Antonio D

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2/19/2026 5:23 PM

I recently tried upgrading one of my company's sites from DNN 9.6.2 to 10.2.1 (but not directly). I first upgraded from 9.6.2 to 9.13.7 and then went through the steps to remove Telerik. Then, I upgraded to 9.13.9 and it looked like the site was still working normally. I then upgraded to 10.0.0, but when I exited the uprgade screen, I was met with this error in the browser:

500 Internal Server Error
The requested Url does not return any valid content.
Administrators
Change this message by configuring a specific 404 Error Page or Url for this website.

I then tried the steps below. However, after each step, I tried navigating to the site, but just got same error above.

restarting the app pool and website in IIS
upgrading from 10.0.0 to 10.1.2
upgrading from 10.1.2 to 10.2.1

Has anyone else run into this error or know how to solve it? Also, I cloned the site I'm working on before upgrading it, so if you have any suggestions, I can start over DNN 9.6.2 and try it out, if need be.

Daniel Valadas

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MVP

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2/19/2026 9:48 PM

The suggested upgrade path is this https://docs.dnncommunity...rade-path/index.html
So from your working 9.13.9 you should go to 10.2.1, then we have a new simpler upgrade processes here https://docs.dnncommunity...st-10.2.0-steps.html which should allow you to upgrade to latest.

Antonio D

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2/20/2026 5:23 PM

I just tried upgrading from 9.6.2 to 9.13.9, removing Telerik, and then upgrading to 10.2.1, but that just resulted in the same 500 error.

johnhenley

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2/20/2026 6:11 PM

Antonio D, do you know if you have any third-party modules on your site? You might get a hint of what is causing the error by looking in the Portals\_default\logs folder. I found that on my site I have been unable to upgrade because some of the modules I use are very old and are using now-deprecated APIs.

Timo Breumelhof.

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Lifesaver

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2/20/2026 6:48 PM

Are there any related errors in /Portals/_Default/logs/2026.MM.dd.log.resources ?

Antonio D

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2/23/2026 12:02 PM

There aren't any third party extensions installed on the site.

I checked the log file and here are the entries from around the time I upgraded to 10.1.2:

2026-02-20 15:07:42,642 [cccweb13][Thread:26][ERROR] DotNetNuke.Data.PetaPoco.PetaPocoHelper - [1] Error executing SQL: ;Exec dbo.MigrateHtmlWorkflows @0, @1
Invalid object name 'STRING_SPLIT'.
2026-02-20 15:07:42,663 [cccweb13][Thread:26][ERROR] DotNetNuke.Services.Exceptions.Exceptions - System.Data.SqlClient.SqlException (0x80131904): Invalid object name 'STRING_SPLIT'.
at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)
at System.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady)
at System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString, Boolean isInternal, Boolean forDescribeParameterEncryption, Boolean shouldCacheForAlwaysEncrypted)
at System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async, Int32 timeout, Task& task, Boolean asyncWrite, Boolean inRetry, SqlDataReader ds, Boolean describeParameterEncryptionRequest)
at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, TaskCompletionSource`1 completion, Int32 timeout, Task& task, Boolean& usedCache, Boolean asyncWrite, Boolean inRetry)
at System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(TaskCompletionSource`1 completion, String methodName, Boolean sendToPipe, Int32 timeout, Boolean& usedCache, Boolean asyncWrite, Boolean inRetry)
at System.Data.SqlClient.SqlCommand.ExecuteNonQuery()
at PetaPoco.Database.<>c.b__315_0(IDbCommand c)
at PetaPoco.Database.CommandHelper(IDbCommand cmd, Func`2 executionFunction)
at PetaPoco.Database.ExecuteNonQueryHelper(IDbCommand cmd)
at PetaPoco.Database.ExecuteInternal(CommandType commandType, String sql, Object[] args)
at DotNetNuke.Data.PetaPoco.PetaPocoHelper.ExecuteNonQuery(String connectionString, CommandType type, Int32 timeoutSec, String sql, Object[] args)
at DotNetNuke.Data.SqlDataProvider.ExecuteNonQuery(String procedureName, Object[] commandParameters)
at DotNetNuke.Modules.Html.Components.MigrateHelper.MigrateHtmlWorkflows()
at DotNetNuke.Modules.Html.HtmlTextController.UpgradeModule(String version)
at DotNetNuke.Entities.Modules.EventMessageProcessor.UpgradeModule(EventMessage message)
ClientConnectionId:d973793f-1d82-4d0a-a1d7-1567282efd73
Error Number:208,State:1,Class:16
2026-02-20 15:07:43,428 [cccweb13][Thread:26][ERROR] DotNetNuke.Entities.Urls.UrlRewriterUtils - System.MissingMethodException: Method not found: 'Void DotNetNuke.Services.ClientCapability.ClientCapability.set_Capabilities(System.Collections.Generic.IDictionary`2)'.
at DotNetNuke.Providers.FiftyOneClientCapabilityProvider.FiftyOneClientCapability.Initialise(IDictionary`2 properties)
at DotNetNuke.Providers.FiftyOneClientCapabilityProvider.FiftyOneClientCapability..ctor(Match match)
at DotNetNuke.Providers.FiftyOneClientCapabilityProvider.FiftyOneClientCapabilityProvider.GetClientCapability(String userAgent)
at DotNetNuke.Services.ClientCapability.ClientCapabilityProvider.GetClientCapability(HttpRequest httpRequest)
at DotNetNuke.Entities.Urls.FriendlyUrlController.IsMobileClient()
at DotNetNuke.Entities.Urls.FriendlyUrlController.GetBrowserType(HttpRequest request, HttpResponse response, FriendlyUrlSettings settings)
at DotNetNuke.Entities.Urls.AdvancedUrlRewriter.ProcessRequest(HttpContext context, Uri requestUri, Boolean useFriendlyUrls, UrlAction result, FriendlyUrlSettings settings, Boolean allowSettingsChange, Guid parentTraceId)
2026-02-20 15:44:05,453 [cccweb13][Thread:23][ERROR] DotNetNuke.Entities.Urls.UrlRewriterUtils - System.MissingMethodException: Method not found: 'Void DotNetNuke.Services.ClientCapability.ClientCapability.set_Capabilities(System.Collections.Generic.IDictionary`2)'.
at DotNetNuke.Providers.FiftyOneClientCapabilityProvider.FiftyOneClientCapability.Initialise(IDictionary`2 properties)
at DotNetNuke.Providers.FiftyOneClientCapabilityProvider.FiftyOneClientCapability..ctor(Match match)
at DotNetNuke.Providers.FiftyOneClientCapabilityProvider.FiftyOneClientCapabilityProvider.GetClientCapability(String userAgent)
at DotNetNuke.Services.ClientCapability.ClientCapabilityProvider.GetClientCapability(HttpRequest httpRequest)
at DotNetNuke.Entities.Urls.FriendlyUrlController.IsMobileClient()
at DotNetNuke.Entities.Urls.FriendlyUrlController.GetBrowserType(HttpRequest request, HttpResponse response, FriendlyUrlSettings settings)
at DotNetNuke.Entities.Urls.AdvancedUrlRewriter.ProcessRequest(HttpContext context, Uri requestUri, Boolean useFriendlyUrls, UrlAction result, FriendlyUrlSettings settings, Boolean allowSettingsChange, Guid parentTraceId)
2026-02-20 18:04:35,858 [cccweb13][Thread:9][ERROR] DotNetNuke.Entities.Urls.UrlRewriterUtils - System.MissingMethodException: Method not found: 'Void DotNetNuke.Services.ClientCapability.ClientCapability.set_Capabilities(System.Collections.Generic.IDictionary`2)'.
at DotNetNuke.Providers.FiftyOneClientCapabilityProvider.FiftyOneClientCapability.Initialise(IDictionary`2 properties)
at DotNetNuke.Providers.FiftyOneClientCapabilityProvider.FiftyOneClientCapability..ctor(Match match)
at DotNetNuke.Providers.FiftyOneClientCapabilityProvider.FiftyOneClientCapabilityProvider.GetClientCapability(String userAgent)
at DotNetNuke.Services.ClientCapability.ClientCapabilityProvider.GetClientCapability(HttpRequest httpRequest)
at DotNetNuke.Entities.Urls.FriendlyUrlController.IsMobileClient()
at DotNetNuke.Entities.Urls.FriendlyUrlController.GetBrowserType(HttpRequest request, HttpResponse response, FriendlyUrlSettings settings)
at DotNetNuke.Entities.Urls.AdvancedUrlRewriter.ProcessRequest(HttpContext context, Uri requestUri, Boolean useFriendlyUrls, UrlAction result, FriendlyUrlSettings settings, Boolean allowSettingsChange, Guid parentTraceId)
2026-02-20 18:46:56,925 [cccweb13][Thread:8][ERROR] DotNetNuke.Entities.Urls.UrlRewriterUtils - System.MissingMethodException: Method not found: 'Void DotNetNuke.Services.ClientCapability.ClientCapability.set_Capabilities(System.Collections.Generic.IDictionary`2)'.
at DotNetNuke.Providers.FiftyOneClientCapabilityProvider.FiftyOneClientCapability.Initialise(IDictionary`2 properties)
at DotNetNuke.Providers.FiftyOneClientCapabilityProvider.FiftyOneClientCapability..ctor(Match match)
at DotNetNuke.Providers.FiftyOneClientCapabilityProvider.FiftyOneClientCapabilityProvider.GetClientCapability(String userAgent)
at DotNetNuke.Services.ClientCapability.ClientCapabilityProvider.GetClientCapability(HttpRequest httpRequest)
at DotNetNuke.Entities.Urls.FriendlyUrlController.IsMobileClient()
at DotNetNuke.Entities.Urls.FriendlyUrlController.GetBrowserType(HttpRequest request, HttpResponse response, FriendlyUrlSettings settings)
at DotNetNuke.Entities.Urls.AdvancedUrlRewriter.ProcessRequest(HttpContext context, Uri requestUri, Boolean useFriendlyUrls, UrlAction result, FriendlyUrlSettings settings, Boolean allowSettingsChange, Guid parentTraceId)
2026-02-20 23:39:05,999 [cccweb13][Thread:8][ERROR] DotNetNuke.Entities.Urls.UrlRewriterUtils - System.MissingMethodException: Method not found: 'Void DotNetNuke.Services.ClientCapability.ClientCapability.set_Capabilities(System.Collections.Generic.IDictionary`2)'.
at DotNetNuke.Providers.FiftyOneClientCapabilityProvider.FiftyOneClientCapability.Initialise(IDictionary`2 properties)
at DotNetNuke.Providers.FiftyOneClientCapabilityProvider.FiftyOneClientCapability..ctor(Match match)
at DotNetNuke.Providers.FiftyOneClientCapabilityProvider.FiftyOneClientCapabilityProvider.GetClientCapability(String userAgent)
at DotNetNuke.Services.ClientCapability.ClientCapabilityProvider.GetClientCapability(HttpRequest httpRequest)
at DotNetNuke.Entities.Urls.FriendlyUrlController.IsMobileClient()
at DotNetNuke.Entities.Urls.FriendlyUrlController.GetBrowserType(HttpRequest request, HttpResponse response, FriendlyUrlSettings settings)
at DotNetNuke.Entities.Urls.AdvancedUrlRewriter.ProcessRequest(HttpContext context, Uri requestUri, Boolean useFriendlyUrls, UrlAction result, FriendlyUrlSettings settings, Boolean allowSettingsChange, Guid parentTraceId)

johnhenley

Advanced Member

Posts: 233

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Engaged Reader

2/23/2026 1:56 PM

Antonio D, this is a database error, and it appears you are running on an older version of SQL? String_Split was added in SQL 2016 which I think is now the minimum version for DNN.

johnhenley

Advanced Member

Posts: 233

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Engaged Reader

2/23/2026 1:57 PM

BTW, "minimum" is relative I guess. The answer is it should be "supported version" of SQL, since SQL 2016 is no longer supported. https://docs.dnncommunity...uirements/index.html

Antonio D

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2/23/2026 5:54 PM

I'm going to try starting over again, changing the sql compatibility level, and uninstalling 51degress

Antonio D

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2/26/2026 11:19 AM

Changing the SQL compatibility level and uninstalling 51degrees before upgrading to DNN 10 did the trick. There are still other errors like old skins breaking, but that's for another topic. Many thanks to everyone above for helping me.

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