7 Days to Die server status checker
7 Days to Die needs both TCP and UDP, which is the detail most port-forwarding guides get half right.
Which ports a 7 Days to Die server needs
The game port is used over TCP for gameplay, while the Steam query runs over UDP on the same base port and the two above it. A rule covering only TCP gives you a playable server that no list can see; a rule covering only UDP gives you a visible server nobody can join.
If it still shows offline
Make sure your router rules cover both protocols and the full port range, not just the single base number. If everything is open and queries still time out, check whether the server is mid-Blood Moon — horde night pushes CPU hard enough that query responses can be dropped, which reads as offline from outside.