can't use FaceTime or messages on iPadPro - iMessage and iCloud accounts don't match

Error message on my iPad Pro reads: "Messages in iCloud not available as iCloud and iMessage accounts do not match"

Also see a message: "Unable to connect to the FaceTime server" when I try to login with my appleID to Messages.

Same situation when I try to login to FaceTime.

Yet the iPad can read Notes, Reminders, Contacts and Calendars stored in my iCloud account.

Not sure how this happened, but suddenly I can't use Messages or FaceTime on my iPadPro, although I could a couple of days ago????

Messages and FaceTime still work on my iPhone and my MacBook Air using the same appleID and phone number. I can communicate between my iPhone and MacBook, just not to/from the iPad.

I didn't consciously do anything to cause this, other than perhaps using a VPN?? I've switched it off and that doesn't help.

To confirm, the iOS is up to date on all devices; I'm using the same appleiD and password on all devices; I'm using the same phone number to initiate new messages on all devices.

I've signed out and in of appleID on the iPad multiple times, shut down and restarted the iPad multiple times, changed the password in case it was compromised.

I can't find a solution that works. Can you suggest anything else to try?