I've been having some problems with my Unraid boot volume, and so I thought I'd restore a flash backup. So I downloaded the backup from unraid.net, flashed it to a new 16 GB Verbatim thumb drive using the Unraid Flash Creator, and rebooted the machine.

But with the Verbatim drive installed, the machine just enters the BIOS and doesn't even try to boot.

Booting from the original flash drive at least boots, but has problems.

Is there some extra step I need to do after running the Unraid Flash Creator?

Are you booting UEFI or legacy mode? If UEFI then no more to do, but if legacy mode then you need to run makebootable.bat in Administrator mode.

I'm pretty sure it's UEFI boot, since the other flash drive booted.

So I tried to run the make_bootable.bat command on my new flash drive, and it failed because it couldn't find K:\syslinux\syslinux.exe, which, in fact, is not there. I reran the Unraid Flash Creator on a separate drive, and there's a lot of stuff (/EFI/boot, /syslinux, /config) missing from my original drive. I checked the contents of the flash backup zip file, and those files are present in the zip file.

I'm recreating the flash drive using Unraid Flash Creator, and will double check the contents before booting again.

Well. Reflashed the drive, and the same thing happened. Unraid Flash Creator just.... didn't copy those files. Will try again after manually copying the files from the zip.

After running Unraid Flash Creator with a default image and then copying the files from the zip, Unraid boots successfully. I opened a bug report on Unraid Flash Creator.