When the fluid pump is working it makes all entitys invisible.I tried to exit the game and load it again but nothing.Then i tried to break the pump and then reopen the game and then it fixes it.If you just place the pump in the world its fine,but when you give it neon energy and connect it to water cooler then the bug happens.

I think this is a Duplicate of #695

It is supposedly fixed in the Dev branch.

You can try this version and see if the problem persists:
Futurepack-1.16.4-21.0.2

Problem fixed.Good job!