Xbox Insider Hub won't let me in the app, says I'm underage, although am not.

Hi,

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Yes but my account is already an adult account, I don't need to change my date of birth because I'm 18. So I don't understand why I can't access Xbox Insider Hub

It is based on the age that was entered when creating the Xbox/Microsoft account. If I remember correctly, there is no way to change your date of birth on your Xbox account. Once the age entered on the account reaches its 18th birthday, you'll be able
to migrate it into an adult account.

I would recommend checking if you signed into the same account on the streaming app as you have the insider hub or if your in project cloudx it should let you,when i tryed the app and logged in with insider hub it wouldn't let me stream my xbox apps because
it was not in my ring region yet so that could be the problem.

This means that your account is not an adult account but a child account, you will need to change the date of birth of your profile, delete the profile and re-enter your profile, if this does not work so you will need to talk to Xbox Support