If you have not already done so, use What to do after you change your Apple ID or password
https://support.apple.com/en-us/HT204071. If doing so does not solve your problem, see below.
__________
Also see this problem that might be yours, an updating Apple ID settings problem. Note that Apple is aware of this problem, but there is no definitive solution yet.
And note that some have solved the problem by signing out of iCloud, restarting their device(s), and signing back in.
See the search results here: update apple id settings unknown error. You'll find quite a few links that are related to your problem. Several suggest fixes.
Use these Apple Support links for more help:
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.