Cannot sign into ring on hubby’s iPhone 13.

Hi. Hubbys iPhone 13, not allowing any sign in, through app or web. have tried different Browsers, uninstalling reinstalling, hard reset. No VPN. Tried with my sign in details and his. Tried resending an invite after deleting his account, but goes straight to no authority. Have tried everything I can think of. Works on my iPhone which is 15ios device, up to date software, ring works on his watch series SE2 and his  iPad 10 gen. Am at a loss