Apple ID suggestion
Can’t update Apple ID settings
iPhone 6s Plus, iOS 12
This may be your problem, an updating Apple ID settings problem. Apple is aware of the problem.
Note that some have solved the problem by signing out of iCloud, restarting their devices, and signing back in.
I suggest you use my search link (update apple id settings) in trying to solve your problem. You will see a number of links that are related to it (some deal with iPhone/iPads explicitly, and others are more general). Note that I have not seen a definitive solution for it. But, some related to the search link claim fixes.
If you want to contact Apple Support to deal with your problem, see:
Get a call from Apple support to help solve your problem using this link https://getsupport.apple.com/?caller=kbase&PGF=PGF63005&category_id=SC0245&symptom_id=23362 Be patient. Phone support sometimes is not available.
Apple ID Support https://support.apple.com/apple-id
Apple Support Twitter https://twitter.com/AppleSupport There may be an hour or so wait.
Apple ID account security for country-specific and region-specific help https://support.apple.com/en-us/HT204169
Get Support: We’re here to help https://getsupport.apple.com/. Go through the options to find the best support option for you.