I never set up a child account, I have played games that are 18+ before but now it says I...

Hi and thanks for reaching Microsoft Xbox gamer's community. My name is Josef.
I'm an Independent Advisor and a Microsoft Xbox user like you.

Hope you're doing great today despite this Chrispy

May I know if you already tried this?

Create a new account that can be considered as an adult account (try using another web browser or incognito mode).

Once done, add your main account as organizer via the link below. (you can see in the new account an "add member" button
https://account.microsoft.com/family/

Please double check that you select your main account as organizer too, not member.

Once successfully added, sign out from your account everywhere and restart your device
Then log in your account again and try again

Hi! I have had this issue before, By any chance is your account marked as a child(under 18)? When i ran into this issue i had to have a parent account set up for them to access the settings as child accounts can not access their own settings

So the answer to this question is basically that every publisher has their own set of rules and if you have a child account set up under the age of 18 on Microsoft these publishers can block all of the features depending on the games ratings. If you have
any questions regarding this I would check the publishers websites or contact them before making your purchase. The only work around right now is to create an adult account if you want your child to be able to play these kinds of games.

As far as I know the account can not be promoted until it shows on LIVE that the account holder is now 18. That would be 3 more years. If this was not the case, it would do parents no good to set up a child account because that child could just change the
birth date to be able to play M rated games.

Were you able to play or install any games before? This error usually shows up if the account is being detected as a child which is when you create the Microsoft account then you enter the wrong birth date by accident or you are really below 18 or 21 years old. If you have a child account, you need a parent or adult account to manage your settings.