I downloaded the Jolly Coop mod, and it worked once before, but after opening the game again the "mod config" button in options menu stopped displaying. I tried downloading other mods and they didn't do anything (I did check the boxes in BOI.) Is this a common problem? Just trying to figure out how to use mods.
edit: sometimes the mods work, but the next time I open the game they stop working. I noticed that whenever I open the game some "preloader_" files are added to my game folder containing code errors.