I recently installed a new shower. It fits in a corner with a plastic type material adhered to the walls and a three sided surround with the door in the middle. All of this sets on the pan.

My problem is that I can't get it to not leak between the surround and the pan. The instructions said to use a caulking with less than 40% silicon. I have tried 3 different types, but they all leak. It seems to stick to the surround and the walls real well but nothing sticks to the pan. I have cleaned the pan well and used alcohol to try and remove any residue from the pan. I've raised the surround three times trying to make sure to seal between it and the pan, but I still end up with a leak because nothing wants to stick to the pan.
Is there a caulking or sealer anyone knows of that might work? I was wondering about a type of strip caulking that could be laid on top of the pan and then set the surround into. Any ideas would really be appreciated.