@davew Check to see if Sign in with Apple Watch is still selected in Settings. If it is not and will not allow you to turn it on. (This happens) first reboot Watch and iPhone and then see if that fixes it. Check settings again. If still a no go, on your Mac, sign out of Messages in iCloud. Resign back in. Give it a few minutes and see if that corrects it. This happens to me quite a bit as Apple monkey’s around on the back end with iCloud stuff. /1