Form submission is not working after migrating SHA1 to SHA256. How to solve it?

Hashing is a on-way encryption. Let's take the example of a password for instance, the user types a password to be store and the system stores a very long "signature" of that password. The system can't know the password from that signature represents. But every time the user types that password, it produces that same very long signature.

Changing the hash algorythm means that that the way to generate that signature changes. Which means that the value store no longer represents that original string and since the system can't decrypt it, there is no automated way to migrate it.

In this specific case, the only way to get back to a working state would be to force all users to reset their password (there is no built-in way to do that in DNN at the moment) but I have known people to use the Newsletter module with a token to do such things.

However any 3rd party module can also use that algorithm which would have unkown effects (I am not sure what you mean by "form submissions" here.

Long story short, although migrating from SHA-1 to SHA-256 is technically a security improvement, considering DNN also uses a salt, the improvement it provides is very very small. See https://docs.dnncommunity...rom-sha-1-to-sha-256|

So unless you HAVE to migrate (required by some compliance regulations, etc.), I would just restore a backup.