iMessages not syncing

I have an iPhone 13 and just upgraded my iPad to 2022 version. Now my iMessages won’t sync. When I try the ‘fix’ of switching off iMessages on my iPad, I get a message telling me ‘iCloud not available because iCloud and iMessage accounts are different’. Well they are not different. I only have one iCloud email. When I turn iMessages back on, I get a message on my iPhone ‘Device Added to Your Account an iPad now has access to iMessage. If you don’t recognise this device, you can remove it in Settings. So I select OK (as the other option takes you to settings), or I go to settings and don’t remove it because I don’t want to remove it. Then, iMessages on my iPad have still not synced. This is just getting frustrating and quite ridiculous. Any help would be appreciated.