Asus Z270F m.2 PCI-E speed won't set to x4, how to? [solved]

[phill9494]

Hey guys, I only just created this account, because I've found a few several questions + answers but nothing really helping me.

EDIT: The SSD I got, seems to bet at its max Speed according to Toshiba, so I am gonna send it back and try with another M.2 SSD

I have a ASUS ROG STRIX Z270 Gaming Mainboard with two M.2 slots (Link: https://www.asus.com/de/Motherboards/ROG-STRIX-Z270F-GAMING/)
This MB offers two M.2 slots, the one right next to the CPU supports SATA and PCI-E mode (speed is not specified here) and second only supports PCI-E (x2 and x4, utilizing SATA Ports 5 and 6 when in x4 mode)

My Problem is however, that I can't get my Thoshiba XG4 SSD 256MB M.2 (full name: thnsn5256gpuk) which supports PCI-E x4

Now I first tried the lower M.2 socket, which can be adjusted in the BIOS between x2 and x4, but whenever I chose x4, the system reboots and sets it back to x2.
Now I have the SSD installed in the upper M.2 next to the CPU, where the speed can't be set and still Crystal Disk Mark says it's running at PCI x2 when it could run at x4.

Can anyone help?
I've googled hours but this seems to be weird...

Thanks in advance!
Phill

 

[phill9494]

EDIT: The SSD is at its max speed according to Toshiba, so I am gonna get another one, sorry for the post