Inspiron 7590 - samsung evo 860 M2 ssd no recognised

Hi all, maybe someone can help.

I have a new Inspiron 7590 that has two SSD slots (no Sata slot as that is taken up by the larger battery). I am trying to use the second ssd slot with a Samsung Evo 860 V-Nand 1 Tb card but or some reasons it is not being recognised after installation. I had seen some posts elsewhere that it is compatible. Does anyone have an idea if it is indeed compatible and if any advice so it can be recognised? I have disabled secure boot in the BIOS but still no luck. 

Is the anything else I can do - any help would be very much appreciated.

thank you