The extension was working fine for weeks . Suddenly it stopped working when we visit the extension tab we were getting the Message "An unexpected error occurred while processing your request. Try again. undefined".
Then we checked the Tableau server status , The TSM controller was in error state (We don't know what caused the issue) . So we restarted the tableau server machine (windows machine - where we installed Tableau server).
It solved our issue . we were able to access the extensions Tab.