m.2 format ssd for an inspiron 15 7559

When we purchased this laptop, I tried to verify with Dell Support what ssd would fit before the laptop arrived so we could order and have it I hand. I was told the m.2 2280 ssd format was correct and ordered the Samsung 850 EVO. After both arrived, I went to install the ssd and the slot was not the same as the layout of the ssd - it only had one notch vs. two for the Samsung 850. I did some research and found out it the mobo was designed for the pcie m.2 ssd. So I sent back the 850 and ordered the Samsung 950 PRO. I installed it and nothing - could not get the laptop to recognize the ssd no matter what. SO here it is, about 8 months later and I still have a $200 ssd doing nothing. Anyone have any ideas? We'd love to put the operating system on the ssd and use the 1 TB hybrid for everything else!