After the recent freeipa upgrades on fedora, the reported "Server Error"
blocking even the login screen.
The logs were filled with such as:
gssproxy {oid ...} Unspecified GSS failure. Minor code may provide
more information, No credentials cache found
Searches report the solution involved rebooting, checking keytab file
access, etc. These didn't help.
What resolved the problem was clearing the browser cookie / data cache.
HTH
Harry