Oh no - the "You do not have permission to play Fortnite" error is back. Epic says they're hard at work on a fix at this very moment, but for now it's up to our own ingenuity to fix the error message and get back to Fortniting. Thankfully, this isn't our first rodeo with this particular issue - we first encountered the rather alarming message back in 2018, so we have a bit of knowledge to impart on what to do.
How to fix Fortnite's "You do not have permission to play Fortnite" message
The most common cause seems to be when an Epic games account is linked to different email addresses or accounts like PlayStation Network or Xbox Live. One easy way to accomplish this is by checking any other email accounts you might've used in the past and finding out which one's linked to the Epic Games account and platform you're playing Fortnite on. Once you've found the culprit, simply unlink it and then log into the correct account on whichever device you plan on using.
If you're having trouble finding the email address that's causing the issue, try them all. Just use the 'Forgot your password?' function on the Epic Games login page and send recovery info to every email address you know you've created. Eventually, you should find a link to reset your password in one of your inboxes, and then you can log in and unlink it.
In short, if you are also experiencing the "You do not have permission to play Fortnite" error, double-triple-check any other emails you've used in the past to find out which one is currently linked to whichever system you want to play on. Unlink it, log onto the Epic Games account you do want it associated with, and connect the two there.