Can you provide the statements you are using to SIGNON with please?
If you are using a script-less SIGNON the most likely cause is that the SAS/CONNECT spawner service is stopped on the Windows server. Check this out and re-start the service if it is stopped.
The SAS Users Group for Administrators (SUGA) is open to all SAS administrators and architects who install, update, manage or maintain a SAS deployment.