Precision M6800, cannot choose M2 Samsung EVO 2TB as boot drive

With a M2 Samsung EVO 2TB mounted in a 'normal' bay unit (Sabretnt M.2 SSD to 2,5 inch bay) i have the same issue. I used Samsung Migration, to replace the now defective original Toshiba HDD, but the whole M.2 is not seen by the latest a26 M6800's BIOS. (So i have NO windows installed).  I used Data Migration before successfully, but some how my M6800 connection or BIOS. BTW, i used the rubber support insert in the M6800's bay.