Are yall on 2 different platforms? Pc/console?
Either way, me and my friend are both on PC and this happens sometimes when 1 of our games crash and we try to load back in. A fix we found was starting a new multiplayer game. Just skip through character creation and load into the mindflayer ship. Make sure both you and your friend are loaded up and standing in that first room. Then, load your old save file. It should pull both of you into the save game. The few times I had to do this, it worked every time.
