If the paint is not gripping it might be because of a few spots of cleaning that may have been missed or in some instances when the varnish hasn’t cured.
If the surface is cleaned properly with Lacquer thinners this should not be a problem.
Recently varnished surfaces. Varnish needs more or less a 6-months curing time before you can paint onto a varnished surface.
An oil treated surface (linseed oil and other oil products) also needs more or less a 6-months curing time.