Users with the impersonator / admin role are not able to impersonate other usersIssue Users are not able to impersonate other users, although having the impersonator / admin role. Clicking on the Impersonate User link will open the Impersonate User popup, but clicking on the Search for user field will return no users.CauseThe issue is caused by bad data in the sys_user_has_role table, which was records with no value in the User field. Look for records where User is empty.ResolutionDelete all the sys_user_has_role records where User field is empty.Related LinksThese records have no function anyway, since a sys_user_has_role record with no value in the User field is meaningless. So there is no harm with deleting them. In order to know how those records were created, we have to look at the instance transactions and logs, and look for the way they were created. If we cannot find any helpful information, or we do not have recent records to investigate, we can import the attached business rule, which does the following: Sends an email notification. You will have to edit the following line with his email address/es, comma separated: mail.addRecipient("<email_address_1>,<email_address_2>"); Prints the function stack trace in the log, so we can see which part in the code has created the record