Counter-Strike 2 server status checker
Counter-Strike servers answer the Source query protocol out of the box, so a failed check usually points at the network rather than the configuration.
Which ports a Counter-Strike 2 server needs
The query shares the game port over UDP. There is no separate query port to forward, which removes the most common failure mode other games have. Being reachable and being publicly listed are different things, though: appearing in the community browser also requires a valid game server login token tied to your Steam account.
If it still shows offline
If the query answers but nobody can find your server in the browser, the token is the thing to check rather than the ports. If the query does not answer at all, confirm the UDP rule and that the server actually finished loading its map.