App Store

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 dealing with iPhone/iPads explicitly, and others being more general). But, note that I have not seen a definitive solution for it. 

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. Sometime phone support 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 one.

Some other things you can try. Do you have access to another WiFi network where you can try? That has worked for several people.

Try a restart.

Restart your iPhone, iPad, or iPod touch         

Try a forced restart.

Reset Device.      

If necessary

Hard reset.        

Do a backup and try a factory reset. Then restore from your backup.

Restore to Factory setting.      

Backup - Restore your device from an iCloud or iTunes backup.      

Perhaps this may help: https://support.apple.com/en-us/HT208856