If you’re experiencing connection issues, try unblocking the following ports: 80, 433, 443, 3478, 3479, 5060, 5062, 5222, 6250, and 12000-65000.
Network ports are basically gates for the internet that allow specific types of network communication. If a port is closed, then that specific communication can’t go through. By opening these ports, you’re letting the launcher and Fortnite get the information they need to run.
Note: The above steps are for Windows 10 and may vary on other versions.