What Dave said is quite true and I would add that your mating surfaces are not clean. After ensuring that the mating surfaces are devoid of any gasket material I would get a clean rag, shop towel, etc and a can of brake parts cleaner and a pair of rubber gloves. Spray a bit of the cleaner on the rag and wipe down the mating surfaces and it will clean the mating surfaces of any oil residue which will allow the gaskets to seal better.