Over the past several years I have experimented with many different types of TinyMiniMicro nodes and thin clients. None of them have had the following problem except for my HP Elitedesk 705 G3 and G4.
When I get my bootable USB stick and install an OS on them, they behave as normal and boot up when they are given power. If, for whatever reason, I need to use my USB and boot into another OS (without writing to the internal disk or changing BIOS settings) then it will stop booting from the internal disk. On the next boot without the USB drive, I get a “3F0” bootable disk not found error. If I then boot again from my usb stick, then my internal drive, which was working 10 minutes ago, is not even detected by lsblk!
Sometimes this will even happen when changing bootloader settings from within the OS in the internal drive. Also this means that I cannot install an OS to a drive when it is on another system and just drop the drive into the Elitedesk. Yet, it works the opposite way and I can take a working (or not working) drive with an OS from the Elitedesk system, drop it into a second system and it works.
I bought the G3 first and assumed the motherboard was just dying. Then I bough the G4 and had the exact same issues. I am wondering if anyone else has the same experience with them refusing to boot. If so, does it only happen on the Elitedesk 705 series or is it also on other series like 800? It could just be PEBKAC after all, but I doubt it, and for the meantime I will be staying away from HP mini PCs. (And yes I have tried fiddling with BIOS setting to get this to work).
Did you try turning fast boot off in bios?