If you get the error message 'EFI USB Device has been blocked by the current security policy' while booting from a USB device, you can fix it in the following way.
- While booting the PC module, press the ESC key repeatedly.
- On the BIOS Frontpage, select 'Administer Secure Boot'.
- Under 'Enforce Secure Boot', select Disabled.
- Exit with F10 to save the change.