If memory serves, this system supports only one internal drive -- either M.2 or SATA, but you can't have both in the system at the same time. If the connector you're looking for isn't evident on the topside of the board, it's absent -- it will not be on the bottom.  
I have a Latitude E5480 with an m2.2280 256gb ssd installed. I want to install a 2.5 inch hard drive, or a msata ssd. I know I can use the wwan slot with a 2242 ssd, but I have a spare msata or 2.5 inch hard drive that I would like to connect to the jsata port. Problem is, there is no jsata connector beside the m.2 connector. It is not broken off, just missing. My cpu is a I7-7820HQ and I assume the motherboard was shipped without the jsata connector. The mother board does look different from the images that I have seen. I am wondering if the jsata connector might be on the underside of the motherboard. It is definitely not on the top side of the motherboard. Either that or this particular motherboard shipped without a jsata connector. Any help would be greatly appreciated before I remove the motherboard and check the underside.
Latitude E5480 motherboard missing jsata