There could be a variety of things that cause this;

1. Not enough adhesive

2. An excessive amount of adhesive (very doubtful)

3. Allowing the adhesive to dry to much before applying the material

4. A board that is not free from dust and dirt and old foam

5. Applying the adhesive to either the headliner only; or the board only (must be a coat on each)

6. Adhesive which the shelf life was out (shelf life--approx. 1 to 2 years)

7. A raggedy headliner board -- and probably a lot of other things that I can't think of at this time.

I would opt for number 3 - the adhesive was too dry when the headliner material was applied. It should be less than 5 minutes after spraying the adhesive, that you apply the headliner material (especially in hot conditions).