Try the manual method of install https://wiki.unraid.net/USB_Flash_Drive_Preparation#Windows_Vista_and_Windows_7
The current list of "incompatible" drives actually contains zero entries (because there are no incompatible drives per se), but rather the requirement is a unique GUID on the flash drive which by and large every flash drive has with the exception of counterfeit or extremely inexpensive drives.
NB, Amazon was found to be selling counterfeit drives (Sandisk) a number of months ago, but reports of that situation have dried up.