Since the Role level risk analysis is working fine can you run the repository Synch jobs and check if GRACUSERROLE table has the required roles reflected in user id. While searching ensure user id is entered in all caps and also the GUID in gracuserrole can be checked for technical name in GRACROLE table. If the user id has the role entries in GRACUSERROLE, then check the selection screen of user level risk analysis. maybe some unwanted default input parameters might lead to the blank output.
A simple eg would be Risk Level is defaulted to Critical will not yield output if there are critical risks assigned so you need to amke it to ALL. Please check on these things and revert if issue still persists.