We recently upgraded our Jira version (Jira 8.7.0) . The users who have not logged in to jira after the upgrade cannot be found or listed under Assignee field or cannot be tagged in the comments with @ . However, the users are part of the project and have Assignable users permissions. Global permissions are checked as well and the jira group has Browse users global permission assigned.
We also ran Re-index and after that the issue still persists.
Please help!