Creating a server on the Forge core, I ran into the problem of generating a world. When I create a world, I knowingly specify the mod type of the world, and when I log in to my server, I see this message:
I don't understand how to fix this error, because, at first glance, everything matches. The mods folders are identical. In the single player world, the game runs smoothly, without any errors. Without mods, the server also works. Starting the world with a single industrial craft mod, I get the same error, and when I start ice and fire, the server loads, but the items are not placed. Also, there are often errors: