Platinum Pfx Polymerase by Invitrogen

I am doing some cloning work so I used Platinum Pfx Polymerase for my PCR. I also used two sets of primers. The results were great for the second primer set but not with the first primer set. I tried including varying amounts of PCR enhancer that comes with the kit but again, no product.

Has anyone used this product before?

Please suggest what I can do to optimize the conditions.

Thanks!