Zinsser peeling off plaster

[SimonPeter]

Just bought a house and redecorating before moving in. The bathroom ceiling seems newly plastered, and I wanted to paint it over before starting to use the bathroom. Started off alright with skimming polyfilla over some minor holes and wiping down the ceiling with a damp sponge. Next day, painted on a coat of Zinsser Ceiling Pro 5-in-1. Within the hour, part of it had started cracking. Next day, large blotches of in one part have peeled off and/or cracked. This is all in the same area, and 2/3 of the ceiling are alright. I tried painting over again and got the same result. What is going on? There should be almost no moisture in the ceiling.

How can I make the thing stick? Skim with polyfilla then sand and paint again? Sand, then skim, then sand, then paint? Or...???

Edit: photos uploaded:

 

[Wayners]

I can't say what has happened although it's not a product I'd use as the application data sheet has no mention of plaster.
It says all surfaces though but I myself would phone the help line first if I wanted to use it.
I'd of given the ceiling a coat of gardz or other primer like acrylic primer undercoat to seal then the 5 in 1 Pro to be sure.

 

[johnny2007]

The plasterers were not paid and sprayed WD40 all over the walls and ceilings...

 

[SimonPeter]

The plasterers were not paid and sprayed WD40 all over the walls and ceilings...

It sure looks like it! Why in the world would the Zinsser flake off and fall off the ceiling otherwise? The previous owners were crooks, for sure.

 

[SimonPeter]

A mate suggested I could try using PVA glue first and then Zinsser on top. Is this advisable?
Could the plaster have been too smooth - do I need to sand it first?
Many thanks!

 

[Grenage]

A mate suggested I could try using PVA glue first and then Zinsser on top. Is this advisable?
Could the plaster have been too smooth - do I need to sand it first?
Many thanks!

No, never put pva on a surface you're planning to paint. Was the ceiling mist coated first? I'd give the problem area a light sand, then mist coat and repaint.

 

[SimonPeter]

No, never put pva on a surface you're planning to paint. Was the ceiling mist coated first? I'd give the problem area a light sand, then mist coat and repaint.

No, it wasn't. The Zinsser ceiling was supposed to be the primer, so I didn't assume it needed to be primed/mist coated before (by 'mist coat' you mean using the final paint in a thinned consistency, right?).

 

[Grenage]

Yes that's right; I always do one on bare plaster/filler. I'd not use your fancy paint though - just some super cheap emulsion watered down.

 

[opps]

https://www.zinsseruk.com/product/ceiling-pro-5-in-1/

It doesn't mention thinning the first coat or using any primers over bare plaster or filler. I would contact Zinsser and see what they have to say.