Cant Get Keep inventory to work on rlcraft

I have a modded server with a couple of friends and we have tried to get keep inventory through the Minecraft commands with /gamerule keepinventory true, but that hasn't worked and we also tried to get keep inventory through the Mod options button in the pause menu (there is a mod where you can toggle things like "keep your inventory after death" and stuff like that, it is called corpse complex) but that hasn't worked either.