I'm afraid that's not enough information. Would you mind please providing more details? If you can, please consider also including which version you're trying to install; what steps you've done; the hosting environment; any errors you see in the log files, etc.

I'm performing a new install of DNN version 9.13.8 on Windows 11 with IIS 10. I'm using SQL Server 2022. I've followed the steps for a manual setup from the installation wiki https://docs.dnncommunity...overview/index.html. I created an app pool and gave modify permissions to the app pool account for the site folder. I created a database and a SQL user login with admin permissions to the database. I verified that the SQL login was working by logging into the SQL with it and was successful. I'm at the first step in the installation wizard and have entered all the requested information (Administrative Information, Website Information and Database Information). When I click "Continue", the error I posted, "..Install/InstallWizard.aspx/ValidateInput 404 (Not Found)", is showing up in the browser console (Edge: Version 134.0.3124.72 64-bit) and the wizard does not go to the second step. No other logs are being generated. 

Thank you for those additional details.  I'm thinking that maybe the environment is not yet ready to run an ASP.NET application.  I have a video that goes over getting your environment ready for a new DNN installation.  I recommend watching that video to see if there are any steps you may need to follow in your environment.  Specifically, you may need to update .NET and/or some related dependencies.  

I'm actively doing .Net development on the same machine (.Net 8). I don't believe that is the issue. The error seems to imply that the webmethod "ValidateInput" cannot be found in the InstallWizard.aspx page. I've looked at the InstallWizard.aspx code and was able to locate the webmethod but the script calling it cannot locate it.

Exactly... When a web API endpoint throws that kind of error in this scenario, that's what I would look into next.  

And I've already investigated that with no success. I've been wrestling with this for 2 days before posting to the forum. I had already gone through that video you suggested, deleted and reinstalled the DNN software and recreated the steps to make a site in IIS. I posted in hopes of getting assistance from persons with a more intimate knowledge of the software. Optimally, suggestions from a successful install on WIndows 11. That seems to be a difference that is not accounted for in the wiki and the installation videos. Additionally, "InstallWizard.aspx" is a DNN source file and not a thing for me to "fix".  

Hmmm... That's odd then.  Do you think your antivirus might be getting in the way?  🤔 

no issues with the antivirus

Can you please share the steps as a screenshot I want to view the settings?