Packet loss is when some of the data packets sent or received between your device and the game server are lost or corrupted. This can cause lag, stuttering, rubber-banding, or disconnections in Fortnite. To fix packet loss in Fortnite, you can try some of the following methods: restart your router or modem, use a wired connection instead of wireless, change your DNS settings, use a VPN service, or contact your ISP.