: This is a leading cause for the error. Players on Windows cannot play with players on macOS or Linux . If a Mac user tries to join a PC friend's lobby, the game will often throw this error because the executable versions do not match.
Make match join idempotent with clearer error codes
If you are trying to join a "No Mod" game but have custom tuning packs or maps active, try unsubscribing or unchecking them in the Mod Manager.