Problem with DUET-REFIND method

Hi all.

I installed debian on my nvme device, then I followed the guide to make DUET-REFIND usb.

So I plug the usb to my system and all is ok, the usb find and boot the nvme disk.

Until here all is ok, but if I reboot the system the usb with DUET-REFIND won’t start nvmb anymore and show me Default sting screen and I’ve to hit enter to Continue.
The problem does not occur if instead of rebooting, I turn the device off and on again.

I think is a kind of configuration problem, but I don’t know how to edit or fix it.

What do you think?