Moving from a different country, iCloud sync issues
My son relocated from Japan back to the US. He took his unlocked iPhone XR and installed his old US carrier SIM card. Calls work/carrier recognition is fine. His iCloud is messed up. Any advice on how to restore/restart? He's restarted both his phone/Macbook, logged out of iCloud - waited - and tried to log back in. He's got nothing. Now, his iCloud p/w is not recognized (or so the message says). Appreciate any help you can shed on this. thanks -
iPhone XR