Why is the car still leaking antifreeze, new gaskets, new reservoir, h

Have you checked the surfaces you applied the new gaskets to, as well as all hose nipples? Look for hair-line cracks and score marks from the removal tools. Hose nipples can be made from a softer metal like brass (which can also be plated to make it look like something harder). Softer metals are very easily scored by a knife or other hose removal tool and you will always get a leak when those marks score a line through the serrated nipples. You will need to file down through the mark, but in such a way that preserves the exact shape of the step. If you muck it up, buy another nipple (cheap). Never assume that because a professional has done the job and tested it, it can't be done in a rushed, cheap manner. I've seen literally hundreds of nipples scored like this and they all deny doing it.