If someone attached mechanical devices that made noise and scrapped the water in your toilet, and you didn't have a clue to why, you might find a new place to squat too ;) That said, try putting the old little box next to the new for awhile, until they get acclimated to the new box. You can also transfer small amount of used litter to the new box, so there's that "sandbox smell."

What the other commentors have said, but also, ideally you should have one box per cat plus an extra. One for four cats is not a good thing, it can cause territoriality and aggression.

If it’s mechanel sounds they don’t like the noise the mechanical arm makes

That’s some “out of the box” thinking there!

I hope you have more than 1 litter box for 4 cats!!! My vet says 1 box for each cat, in different locations.

I have a litter robot and none of my 4 cats have issues. I started by leaving it unplugged for the first week, while letting them explore and use it after i dumped litter and previously left turds into it. The next week, i’d wait till they weren’t using it for 10 mins, then plug in and run it manually where they can observe it run from across the room, then unplug. The third week I left it plugged in and within a day they got used to it. My biggest issue is they like to hop in it while it’s self-cleaning and ride it like a damn amusement park ride. But 4 cats, one litter robot and they don’t mess anywhere else. You need to acclimate them right. Don’t be lazy!