need to verify account to play 18+ games

You may also need to update the date of birth listed on your Microsoft Account/the Microsoft Account that's linked to your Xbox Live account if its incorrect and you are over the correct age to play games that are rated M for 17+ audiences or often 18+ audiences
in other regions such as Europe with the Pegi ratings or in Japan for Cero D/Z.

Go to https://account.microsoft.com/profile/ and select 'edit date of birth.' I think there's a limit to how often you can do this in a given time frame but please double
check that your DOB is correct on your account and adjust it as needed.

Hi,

You might want to check your account online privacy settings
https://support.microsoft.com/en-us/help/4482922/xbox-one-online-safety-and-privacy-settings-for-parents-and-kids


You can also do that thru Xbox, from the Guide > System > Settings > Account > Privacy & online safety

If you’re not the owner of an adult account then an email will need to be sent to the adult account allowing for an exception for the content you desire.

This link should help https://beta.support.xbox.com/help/account-profile/manage-account/request-update-account-information

Thars for your email not your ms account/xbox account

as verified before you need to be 18 and it cannot be changed afterwords