Yesterday I had a problem where when I tried to log in I was getting "Invalid Credentials" error message. Tried restarting IIS and the server without success. I finally restored the "App_Data" folder and was able to log in. I used the application the remainder of the day without issues. Today I again have trouble logging in with a different message. Today I get "The server was unable to process the request due to an internal error.
See the security advisory here connectwise.com/company/trust/security-bulletins/connectwise-screenconnect-23.9.8
You should shut down your server immediately and begin incident response procedures. The attackers likely have full admin access to your screenconnect instance and could deploy ransomware to any devices in your instance. The symptoms you described are consistent with the recent compromises in the news. There's an advisory here with some information on how to upgrade from older versions ConnectWise | Trust Center | Advisories
It sounds like your server may have been hacked. Did you install the patch?