A friend of mine based in Paris, France, encountered this issue, and we’ve been troubleshooting this bug together. I’m located in China while he lives in Paris.
We have attempted numerous fixes one after another, including modifying DNS settings, flushing the DNS cache, connecting via VPN, disabling the Windows Firewall, launching the game with administrator privileges, switching to the game’s beta branch then reverting back to the stable release, yet none of these solutions worked.
We tried one final troubleshooting step: I logged into his Steam account on my PC and launched the game, but it still showed offline mode. In contrast, logging into my own Steam account on the exact same computer worked perfectly fine.
Later, my friend signed into my Steam account on his computer and booted up No Rest for the Wicked. Surprisingly, my account could successfully connect to the backend servers and play online without any issues on his machine.
From this, I deduce there is a bug occurring during the Steam entitlement verification process tied to his account. This permanently locks his account into offline mode on every device he logs into, preventing it from retrieving a valid authentication ticket and resulting in failed multiplayer validation attempts.