The idea of all paints is the adhesion between the paint material and the painted surface. the reasons for peeling can be one of the following:
1- not cleaning the surface before painting
2- not giving the paint layers enough time to dry
3- using wrong material like using internal paint for external walls
unfortunately, the old paint should be removed then you should clean the service and treat it with good primer paint to receive the material.
You have to be should that the wall is very dry before applying the new paint.
If still humidity in the wall, then it should be treated with some glue paint to block the effect of humedity.