Can you go into your BIOS and check the following settings:
- BIOS > Advanced > PCH Configuration > PCI Express Configuration > AUTO
- BIOS > Advanced > System Agent Configuration > NB PCI-E Configuration > AUTO (for all of the slots)
- BIOS > Advanced > Onboard Devices Configuration > PCIEX4_1 and Front USB3_34 / back...... configuration > AUTO
- BIOS > Advanced > Onboard Devices Configuration > 4-Way Configuration > AUTO
....or the highest generation/speed available. I use AUTO for all.
These are how I have mine set. Sometimes it seems the speeds (GEN#) get screwed up, and this may affect your M.2, because it shares resources, at least with one of them.
Davemon50