Upgraded from 11.6 to 12.2, custom hostname for Opmanager not working

Upgraded from 11.6 to 12.2, custom hostname for Opmanager not working

I've just upgraded from 11.6 to 12.2 (Essentials) . I can log into the server using the actual hostname of the server. But can no longer connect using the custom host name.

The SSL Cert (which matches the custom hostname) is still working, as can see it load with the local (incorrect) hostname.

Even when connecting to the custom hostname, the cert loads and reports valid, but nothing else loads- no login screen.

It seems like a host header entry is missing somewhere perhaps?

                New to ADSelfService Plus?