Sometimes when trying to view user sessions in the access management console, the console fails to display any users but rather displays an error message:
“An error occurred. Try performing the task again. If the problem persists, contact support.” Then under details “Unknown error occurred”
This typically indicates the console is having trouble enumerating users or getting valid data back from the data collector. I then found that clicking on each individual server to display users pinpointed which server was not able to provide information as it popped up with its own error unknown message.
I then stopped the IMA service on this server which does not impact users sessions in progress (but will prevent new sessions from being directed to that server). I then ran dsmaint recreateLHC which recreates the local host cache, a subset of the datastore. Then I restarted IMA and made sure the server was back in the farm (verify with theQFARM command)