Fix Guide

If multiplayer is not working, start by assuming one small mismatch is breaking the session.

Most co-op failures are not mysterious. They are usually one of a few things: one player is on a different version, one storefront build updated earlier, one host session needs a clean restart, or the party is testing too many variables at once.

Checklist 1: cut the obvious mismatches

Confirm that every player finished downloading the latest update

Fully close and relaunch the game on every machine

Make sure nobody is on a test branch, preview build, or stale session

Try one host and one guest first before rebuilding the full party

Subnautica 2 cave passage scene in warm orange light. — If you troubleshoot with too many players and too many platforms at once, you waste time fast.

Checklist 2: narrow the problem down

Ask one simple question: does nobody connect, or does one specific player keep failing? If the whole lobby is dead, focus on host session freshness, patch state, and global service issues. If one player fails while the others connect, focus on that player first and stop changing the whole party setup around them.

When to escalate

If you have already matched versions, restarted everyone, tested with only two players, and still cannot connect, stop improvising. At that point you want a proper bug report or an official support path, because random extra changes can make the real issue harder to spot.