"Connection to the server was lost" message when i try to connect to my hosted server

[Jachoslav]

Hello,
i kinda have a problem, when i want to start a modded multiplayer session, when i create my character and try to load into the game, it gives me a black screen and says "Connection to the server was lost" and gives me a "Quit to desktop" option.
One of my theories is that my pc can't handle like 30 mods loading in (Maybe i am just stupid and it's the case) but i tried removing most of them and it still doesn't work...
I am playing on the newest build.
Anyone can help?