Please Reach Out To Me.

As Pandy Yato said, You will need to speak to your parent/caregiver and see if they can let you play because adults make those changes.

Ask your parent guardian to sign into the parent account and review the family.

If your account shows up there, your parents need to go to
https://account.xbox.com/settings to allow your account to play with people outside of Xbox Live (if you intend to play Cross Platform in Fortnite).

Also, Multiplayer has to be enabled on your account as well as the ability to see community created content.

Only adults may make such changes to their family account, you will have to speak to your parent and see if they change your settings and allow Fortnite.

The enforcement team doesn't use the forums and we can't help you with suspension issues. Please see enforcement.xbox.com

You can always submit a case review if eligible. Here is the info on how to do that: http://enforcement.xbox.com/home/howto#sub-topic0-6

Device bans are not issued lightly, and occur when a particular Xbox console or Xbox on Windows device is used to violate the Code of Conduct in an egregious or repeated manner. Once a device ban occurs, no account can connect to the Xbox Live service from
the affected device. Given the severity of this action they take each device ban extremely seriously, and only take action after a lengthy investigation.

A common misconception is that a certain number of reports will result in an automatic suspension. According to the myth, even if you haven’t done anything wrong someone can get you suspended by encouraging players to file many complaints. This is completely
untrue.

XBLPET investigates complaints and takes each report into consideration when making an enforcement decision, but a certain volume or frequency of complaints doesn’t guarantee a suspension. We take an evidence-based approach to enforcement and take numerous
factors into account when considering issuing a suspension. The context around the content or activity is particularly essential and drives our decision-making process. Simply put, there is no magic formula that instantly results in a suspension.

Despite what some may claim, XBLPET will never ever ban anyone “for no reason”. Suspensions
always occur as a result of a specific Code of Conduct violation.

If you're looking for some new gamers to play with, the "Community Chatter" section may interest you:

forums.xbox.com/.../134.aspx