If you already joined RoomSync through an invitation link and are now being asked for a passcode, this means that RoomSync doesn't recognize your account.
You can register for a RoomSync account using Facebook, Google and Apple sign in options. When you first create a RoomSync account, it is linked to one of these options. If you logout of RoomSync and then register with a different Facebook, Google or Apple account, we won't recognize it and will ask you to enter a passcode to ensure you belong in the matching network.
To resolve this issue, logout of RoomSync, go to the Sign In tab and try signing in with any Facebook, Google and Apple accounts you have access to. When you sign in with the correct account, you won't be asked to join a network or enter a passcode.