Please provide us with your laptop model, OS, XDJ-RX firmware version and version of Rekordbox you're using. The more specifics you provide, the more the community can assist you.
Basic Troubleshooting
Have you checked your Firewall settings? Sometimes, especially after installing system updates, firewall permissions can change and if you happened to have disabled your firewall for performance reasons, an update will often enable it once again.
Have you tried a different LAN cable?
Cheers.