After you register DCS:SA with UMC, then later restart the DCS:SA Server you cannot log into the Management Console.
SDCSS could not log you on. Make sure your username is correct...
When DCS:SA is registered with UMC the certificate is replaced.
The Management Console is still attempting to use the old certificate from before DCS:SA was registered to UMC.
You must remove the old certificate and log in again to allow the Management Console to pull the new certificate.