I had a very similar issue recently on an intel X99 setup while experimenting with different drives and such.
I ended up shutting down, removing all drives (sata/usb/m.2), clearing CMOS by switching PSU off, removing battery, and also pressing and holding CLR CMOS button for 10 seconds.
Restor power, boot into BIOS.
load optimized defaults, save and exit.
boot into BIOS, adjust date and time.
find BOOT tab, look under setup mode for a button called SECURE BOOT.
you want to clear/unload/delete all the keys.
You should see things like PK, KEK, DB, etc..
BEFORE DOING THIS---- MAKE SURE you have an option up top called "INSTALL DEFAULT KEYS"
If you have this option, go ahead and on each key spot, press the delete otpion.
After done, hit install default keys.
F10, save and exit.
while back in BIOS, verify there are keys present in the boot section you just were in. If all good, hit power button to shut down.
Toss your drives back in, and see what happens.
You may need to play with the BOOT menu in BIOS to restore booting ability. maybe UEFI only, or find something like "both Legacy and UEFI"