where the user does not know the password to the Keychain, the best thing to do is to make a new one.
Yes, you will have to start again but that is not the end of the world, just makes things a little slower for a while until the KeyChain catches up with you.
Once you have a good password for the keychain, change the password on the user account to the same thing.

One of the causes of the problem is when the user changes the logon password and forgets the one that originally set up the KeyChain.