SEPM says clients online but local client says not

Here's an interesting one.

I've just upgraded our SEPM from RU6 MP3 to 12.1 RU2 upgrade went ok and clients checked into the manager.

SEPM is reporting that the clients online and checking in but when I check the local client on the SEPM it has no green dot and troubleshooting is showing offline.

I can't update the sylink file as the original installation was done by someone else and nobody seems to have the client stop/uninstall password.

Local client is now upgraded to 12.1 RU2 and initially checked in and now reporting offline again. All Defs are up to date.