Unable to login from remote except for the service account (4378440)

 Both server and client are running version 5.20.0.5. The only user account that can authenticate successfully against the GPOAdmin server is the service account used to install the upgrade. Even members of Groups that are configured as admins are not able to logon remotely

Typically when GPOADmin starts up it sets its own SPN, and GPOADmin 5.20 would default to server and port SPN style unless it was still set in the registry to use the old format. This could be the mismatch if the updated config file did not match the registry entry which is also outlined in the KB below, or if the service account did not have permission to update the SPN.

GPOADmin 5.19 and 5.20 will use the Server and Port SPN style by default unless overridden by the registry and config file settings, or if you have an older version and the service account cannot update the old SPN value. It is important that the registry and config file values match on all servers for the product to work as expected.

https://support.quest.com/gpoadmin/kb/4292534/error-message-connecting-either-the-target-name-is-incorrect-or-the-server-has-rejected-the-client-credentials