View: httpstake a picture of the slot in the tablet
upload to imgur.com and post the link here.
my guess is you looking at it wrong
View: httpshttps://en.wikipedia.org/wiki/M.2#Form_factors_and_keying
you mistaked key with the slot. B & M key work in B slot or M slot.
but your tablet only build for taking SATA m.2
and my guess is you put the 980 pro upside down. since it is a M key(x4) not B(x2)