The terminal service client %1 has provided an invalid license
Had a problem with an old citrix environment today where they were running metaframe 1.8 on a Windows 2000 server that was also the domain controller.
They had rebooted the box and ICA clients were unable to log in. RDP sessions were fine.
There were no errors getting logged at all in the event log. After some playing about and trying different things I re-activated the Terminal Server licensing service and then restarted it and got a message about the database was corrupt. Entered all the CALS back in but this still didnt resolve the issue although now we were getting
The terminal service client %1 has provided an invalid license
in the event log
With some further digging I found an article that talked about deleting the following registry keys on the server that is running the licensing service.
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\TermService\Parameters
Certificate
X 509 Certificate
X 509 Certificate ID
This then requires a reboot to kick in. After rebooting the box this resolved the issue and the clients were able to connect again