BIOS Update fails - Secure flash check failed

I have an older AB350M Pro4 AM4 motherboard with a Ryzen 3 2200G currently installed. The current BIOS version is P4.50. I am trying to upgrade the CPU to a 5600G, which requires at least BIOS version P7.20 to support the CPU.

In order to update to 7.20, I am required to first install the 7.00 bridge BIOS update. I downloaded both BIOS versions and extracted the 7.00 file to a recently formatted FAT32 thumb drive. Booted to instant flash and it found the file just fine. I selected the file and clicked yes to start the update. After a second or two it returned the error "Secure flash check failed."

By the way, yes I did disable the CPU fTPM as required for Instant Flash.

I tried several different USB ports, all of them 2.0, with no luck. I also tried several different downloads and different thumb drives still with the same error.

Since the thumb drives wouldn't work I also tried the internet update. It also failed, saying to check the network settings, which were already set to match the settings indicated.

I've seen some very old posts with this issue but none of them had any good answers. The suggestions that were given aren't applicable since they referred to a downloaded BIOS updater, which is not currently provided.

Hello!

Please, reset the CMOS before updating the BIOS!