Thank you, I solved this problem by placing original ssd to second slot and new SATA ssd to the first slot. It works, but I have to change boot options in BIOS as well.
I have Vostro 7590 with big (97Ah) battery. I added second SSD to m2 slot (WD Blue M2 2280 512 Gb), but I can't see it even in BIOS. Any suggestions? [IMAGE]
Dell vostro 7590 second SSD not working