Enshrouded server status checker
Enshrouded uses two consecutive UDP ports and answers queries on the second, which is the one people miss.
Which ports a Enshrouded server needs
The game port is what players enter; the query port sits immediately above it. Both are UDP and both need forwarding. Because they are adjacent, a range rule covering the pair is the simplest way to get it right.
If it still shows offline
If both are open and the query still times out, check the server slot configuration and that the save finished loading. Enshrouded's terrain data is substantial on a well-developed world and the server does not answer until it is ready.