Did you fix it in the end? I was wondering what size snaps you were using as I just use the standard size 20's and last week snapped through a nappy that was Pul, Microfleece and TWO layers of minky and it worked fine. I had to push down really hard but it was ok. I was worried that it would be too thick.
I've read also that some people also stab through where you want the snap with an awl first to make a hole, then put the snap pieces together and press (as if you were using the snap pliers). Fortunately i didnt need to bother with that though.
Mum to busy boisterous boys! Mr Z (April '09) and Mr L (Jan '11)