Hi ShaneL,
According to your description, have you checked if the Legacy Mode has been disabled?
Few steps you could try to follow:
You could do it by Restoring Factory Keys:
BIOS - Security - Secure Boot - Restore Factory Keys - Enter
BIOS - Restart - OS Optimized Defaults - Enabled
BIOS - Restart - Load Setup Defaults - Enter
Go to BIOS - Main and check if UEFI Secure Boot is ON.
As far as I know it may take several reboots to enable secure boot in the BIOS .
Then please check the registry below:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecureBoot\State
UEFISecureBootEnabled value=1
Best Regards,
Carl