Hello,
To figure out exactly why it is still treating you like a child account I need to know what happens when you try to log into the Xbox privacy and online safety website using that account.
- Does the site actually let you see and click a bunch of allow and block toggles for joining multiplayer games, or does it immediately kick you over to a family safety support page explaining that you need a parent to manage it?
- Also, did you just recently change your birth date on your Microsoft account to try and fix this, or was it already set to over 18 when you first created the account?
The system usually permanently locks in your child status based on the original date you entered even if you change it to an adult age later, so knowing this will tell us exactly which method we need to use to force it unstuck.