Thanks, just sent feedback to apple so hopefully if everyone does the same, this gets addressed soon. I also noticed "iPhone cellular calls" in FaceTime had disappeared, and also handoff and instant hotspot are no longer working. Everything is still working between the iPad and iPhone in this regard. So I put an app-specific password in the pop-up box and it only asked twice and went away, now the "iPhone cellular calls" option has returned but when I tick it, I get a message telling me to login to the same iCloud account on both the phone and mac - even though they already are. This is all very strange.