you cannot play on realms because of how your Microsoft account is setup

Hi, 

My sons Minecraft account on his xbox has just started with the following error message when trying to access his realms 

you cannot play on realms because of how your Microsoft account is setup

We have followed countless tips on enabling all settings etc, reinstalling software but nothing fixes it. Oddly the same account used on his android phone works fine so it seems to be an issue with xbox. Please can you advise on a fix? Thanks