Fortnite

Sometimes, Fortnite or other Epic Games titles have a "Server Offline" under them.

A- Causes:

1- After an update immediately,to usuallysome of the epic games (mainly Fortnite), sometimes Epic take servers offline for maintenance.

2- When there is an outage in the service ( problem with hosting servers or data centers etc etc...)

B- How to proceed:

Step1: Check server status at https://status.epicgames.com/

if everything is ok, and it shows a screen like this, indicating that everything is operational then proceed to step2

Step2: report issue to Nest Technical while saying that you checked the status at Epic Games

example report: "Fortnite server offline, checked server status, everything is ok, but the server is still offline" 

If Step1 shows something like this 

then keep refreshing to check when the maintenance is over.