Problem with covering
The problem with covering of the paint is the excessive transparency and fail in full covering of the primer coat.
A poor mix of paint, the excessive thinning, the applying of the top coat paint on an unprimed and absorbent surfaces or not using the appropriate number of layers.
Clean the old paint layer with the help of sanding paper. Thin the paint as it is given in its instruction and mix until getting homogenous solution. Apply at least two layers waiting 3-4 hours between each layer.