According to Epic Games, Fortnite is currently experiencing a period of “degraded quality” that will affect all actors. You may have difficulty connecting to the game or participate in games because of that. You might also have problems with your locker or receive messages informing you that you are not allowed to play Fortnite. At present, we think that all these different problems are caused by the same problem.
According to the Fortnite State page, EPIC is aware of the problem and strives to solve it:
Update – We are still actively working to solve these problems.
Please note that if your friends do not appear in your friends list, they will be again when these problems will be resolved.
March 17 at 19:23 UTC Investigating – We are currently studying connection, connecting, object shop, parties / friends / messaging and game services. We will provide an update when these problems will be resolved.
March 17 at 18:46 UTC
The problem also affects features such as your friends list. Therefore, if you connect and no one is on your list, it will be solved as soon as the general problem is solved. You really can not do much on your side, because the problem occurs on the game servers, it belongs to Epic to solve it as quickly as possible.
We do not know if the problem is somehow linked to the 12.20 update that came earlier in the day and introduced helicopters, and the new limited time mode called Spy Games.