SEP Upgrade from 12.1.1 to 12.1.4 - all clients showing offline

All,

I've  upgraded SEP from 12.1.1 to 12.1.4, retaining existing settings, however all the clients are showing as offline in SEPM. I can log into SEPM fine, and see all the previous settings, but all clients are offline. The server itself is showing as online.

SEP 12.1.4 is on the same server as before, with the same IP and name - I'm guessing the existing sylink file on the clients wouldnt need to be upgraded? Or would a new sylink file need to be deployed?

Checked the troubleshooting tool on a client and it says "Could not connect to the server". Port 8014 isn't blocked & windows firewall is also disabled.

Any help towards identifying what the issue may be would be appreciated.

Thanks,

Evren