I strongly recommend a complete and valid backup of the firmware. Try Intel ME tools 15, flash programming tool
fptw64 -d spi.bin
If that gives an error message try dumping the different regions separately:
fptw64 -DESC -d fd.bin
fptw64 -ME -d me.bin
fptw64 -BIOS -d biosreg.bin
After confirming a valid backup (at least of the bios region and flash descriptor) it’s either finding the corresponding store / setting in NVRAM and changing it back or emptying the complete NVRAM.
Similar problem, fixed by rewriting one corresponding byte in NVRAM: