I've got a few suggestions, not sure if they'll help, but it's worth a shot
Try changing your rendering system.
If that doesn't help, try uninstalling the game completely (By deleting the FeralHeart folder) and re-installing it
If it doesn't work, go to c/feralheart/media/particles (or, in some cases, c/feralheart/media/sky)
Look for .particle files that end in _0,_1,_2,_3 or similar, those are duplicated particles and they cause the game to crash. Delete them.
Sometimes it's a server problem, where the servers have to be restarted, try creating a temporary account or logging on another account of yours.