I'm aware that the rendering of entites from other mods (supported or added by users) is still not working on multiplayer, both inside the cages and in JEI.
I'm working on fixing it, but it's not so easy to find out what's causing the problem.
Nevertheless, sampling and getting the drops still works, but without visual feedback (The One Probe and Hwyla still works too, if you want to know the growth %).