are these the push-pins like this ?
If they are, then yes they should be very secure. Id recommend undoing them then trying again. You should hear a "click" when they do push in properly.
Also, when you put them in put one corner first then do the opposite corner (diagonally) and not the one next to it.
edit: to undo them, just get a flat-head screwdriver and turn the little black bits in the direction the arrow shows (counter-clockwise on mine) and they should come out easily.