A few different things can cause paint to peel on the ceiling including moisture, humidity or improper painting preparation.
If you've just newly painted the ceiling and the ceiling paint is peeling it could be caused by improper painting prep.
If the surface was not clean and not dry and primed first before painting then the paint may not stick properly and peel off.
So make sure that when painting the ceiling or any other surface to be sure the surface is clean, dry and you've primed the surface with the proper primer before painting.
If you have done that then you may have put the paint on too thick at a time and need to paint it thinner.
But if the paint was already there then it's likely humidity in the room that rises to the ceiling and then leads to the pain peeling.
You'll need to scrape the old paint off and then prime the surface and repaint.