I'm trying to play modded with my friend and it wasn't working, so we left and turned off some mods that might not work on multiplayer. Then when i tried to get back into the game I just crashed the second I started up the game. I tried turning off every mod and having only a couple of them on, but I can't open the game. I restarted and was able to load the game, but multiplayer still wasn't working. So I left again and the problem keeps on happening.
Solution
I saw that you're using the Industrial Evolution mod, it has issues with Dedi/MP session, but there's a workaround on our Discord server, you will need to use an SML dev build though, so I'm not sure if you're comfortable doing that