Space Marine 2 Co-op Not Working: Fix Join & Invite

If you cannot join a friend in Space Marine 2, the cause is almost always on the connection or a setting — not the game itself. Saber’s own support guide notes the invite involves two connections, so the block may be on either end, and it is often the host’s side.

Fastest fixes (in order)

1. Check crossplay on both accounts. Open Settings → Gameplay on both machines and confirm crossplay is set the same way. If one player has it off and you are on different platforms, the session simply does not appear — no error, just invisible.
2. Check NAT type. Strict NAT blocks incoming session data. PC: Windows Settings → Gaming → Xbox Networking. PS5/Xbox: Network status. Enabling UPnP in the router usually fixes Strict. Open works with everything; Strict frequently fails.
3. Use the in-game invite code, not the platform overlay. Open the Lobby Menu (top-right), copy your session code, and have the guest enter it from the same mode’s invite menu. Platform invites fail more often after updates.
4. Change the game mode, then switch back. If a friend cannot load in, have the host swap to another mode (Operations or PvP) and back; sometimes the session needs a reset.
5. PC: disable Steam Overlay and cloud saving for the game, then retry.
6. Restart the game on both systems and confirm both are on the same version (a post-update mismatch breaks parties).

If it still fails

Change DNS to Cloudflare (1.1.1.1 / 1.0.0.1) or Google (8.8.8.8 / 8.8.4.4) and restart. For cross-platform groups, confirm every player has crossplay enabled before remaking the squad. Campaign, Operations, and Siege share the same in-game invite code system, so the Operations mode guide steps apply to every co-op mode. Full co-op mechanics are on the co-op guide; if invites fail across every mode, check official service status before touching router ports.