I need some help with a modded server

I’m using spongeforge 1.12.2-2838-7.4.7 on my server, minecraft version is 1.12.2. The problem is that the bosses in Advent of Ascention 3 won’t spawn on the server. I tried to do it in singleplayer on a new world with the same modpack and it works fine. Is there some config that i can change to fix that problem?

Bosses are summoned by throwing an item on the ground, then after a few seconds it should spawn in the same place.

I appreciate any help you can provide.