NUC7I3BNK: Crucial MX300 275GB SATA M.2 SSD not recognized

Bought an Intel NUC7I3BNK and a Crucial MX300 275GB SATA M.2 2280SS SSD.

Although it is listed as compatible at Crucial MX300 Interne SSD 275 GB M.2 2280SS CT9857401 | NUC7i3BNK | Crucial DE  , the SSD is not recognized in the BIOS.

Already updated the BIOS to the latest version 0057. Details from BIOS setup:

- Advanced -> Devices -> SATA : SATA is active. SATA Port shows "[Not Installed]"

- Advanced -> Devices -> PCI : M.2 Slot is active. M.2 Slot shows "Not Populated"

I have no other M.2 SSD available to test if the problem is related to the SSD or to the NUC.

Any suggestions?

Thanks in advance.

Dirk