I was banned from Fortnite for unknown reasons...what do i do to get it back?

As Fortnite is not a Microsoft game and we have no control over Epix policies or account system, you would have to ask them. I recommend you check your email where you may have details

https://www.epicgames.com/help/en-US/c-Category_Fortnite

First no one has the power to ban you except the enforcement team.

Second even if someone reports you does not mean you will get a suspension on your account unless you did something that was against the code of conduct which can be found here https://www.xbox.com/en-US/Legal/codeofconduct

If you feel that your suspension is unwarranted you can sign into the account that has the suspension on it at enforcement.xbox.com and if the suspension is eligible you can file for a case review.

My son has just received a ban from his Xbox account and it emailed him a long list of possible reason but no exact reason. I have contacted Microsoft several times and they tell me I have to get on the forum to talk with the enforcement team so I am trying
this. His gamer tag is Low Gamerscores and I would like to know what I can do to get him access back to live and if that is impossible then get some explanation as to what he done to deserve a ban and what is a better solution than forcing parents to pay for
another live account when they get no reason that their child was banned.

Hey Ashley!

Nice to meet you! I'm Darhyl, a fellow gamer. I'm sorry you are experiencing this. I am here to help.

To answer your inquiry, if your refund request was denied from the refund webform, you can still dispute the decision by replying to their email and help them understand that your refund should be granted.

You've got nothing to worry I had a similar issue before and had my refund approved after I disputed it to the refund webform.

If you have recently submitted your refund request via the refund webform, your refund will be accommodated within 72 hours.

Thank you for your time. I hope you have a great day!

Any information about the ban would be listed at
http://enforcement.xbox.com You would also need to check there to see about submitting a case review.