An up-to-date installation of SEP for Mac (Symantec Endpoint Protection for macOS) will display "Definitions are outdated" after upgrade to version 14.2 RU2
SEP 14.2 RU2 for Mac uses a different version of the LiveUpdate content, and requires updating after the client software is upgraded
Run LiveUpdate after upgrading SEP for Mac to version 14.2 RU2