This is most likely an issue with a mod itself. I have no experience with MP, but you could try loading each mod individually until you find which one is causing the crash.
A lot of times this issue is because your Windows security is set to block certain .dll files, and is blocking the mod's .dll. To fix this, use these instructions:
"If the game crashes on startup after you have installed a mod, you can try unblocking the mod's .dll files. Open the mod folder in your modules folder, then navigate to bin -> Win64_Shipping_Client. Right click on the .dll file and select Properties. In the popup window, check the Unblock checkbox at the bottom. "
However again this is a seperate issue to this thread's, so feel free to make your own post about your issues.