Paint isn't sticking on the freshly down wall

one word : moisture. thats the problem not the paint or not the painter. the wall if its been done 3 months ago but it is still possible to have moisture inside it and it will wear of any possible paint. i hope this helps

Yes, moisture vapour, or water/ dampness will stop the paint adhering to surface. First it best to find out if water or possible moisture is coming from outside or next door. From my experience though, that's easier said than done. First scrape or sand back the area. Not too aggressively, but enough to remove bubering paint. Remove dust, and seal with Zinnsser damp seal, or Ronseals damp seal, or even P.V.A glue. ( Best used a dedicated product fir this promblem) Oil based products or Shellac based product could work better. Leave to dry and repeat. Once dry roller on 2 fresh coats of you wall paint.

I had that problem before where dulux matt was peeling off on mist coat 50/50. One thing is like one of the answers suggest moisture but most of the cases use Armstead trade white matt 50/50. Cheap paint and really good on mist coats. Even if you have moisture on wall it shouldn't peel off but you will just see damp soots where paint hasnt dried completely.

If you are applying a mist coat to new plaster was the plaster fully dry? If not, then the new plaster is not sealed and will fail in those areas either flake, bubble, or peel. Scrape right back to new plaster sand the area and edges to feather in and leave to dry. Seal with a zinnser product and leave to dry. Top fill and rub down where necessary. Repaint area only with wall colour (spotting in) leave to dry. Re paint whole wall again to finish standard.