I can’t directly reply to your thread in the forum because the thread is closed. There are a couple of things I can think of regarding your problem. First, I assume you know that there are 2 generations of the ONN device. The newer one says “4K Streaming Box” (Robot or human?). If this is the box you have, then it should work, assuming you have a compatible flash drive. I have found that the new ONN box is less “fussy” about what flash drive you use than the Firestick, however it won’t work with just any flash drive.
As I understand it, you already have another ONN box that is working with a flash drive. To rule out the flash drive being the problem, I would suggest that you power down the working ONN box, remove the flash drive, and try it on the “bad” ONN box. If it recognizes the drive, then it proves it’s the make/model flash drive that’s the problem.
While I don’t believe that plugging the flash drive from the good box to the bad box will change any of the data on the flash drive, to be safe, you might want to make a backup of the drive from the good box before plugging it into the other box. I use ImageUSB (https://imageusb.en.softonic.com/) to write a backup of the drive to a hard drive. If nothing happens to the flash drive, great, just delete the backup. If it did change the flash drive, then use ImageUSB to write the backup image you made back to the flash drive.
Good Luck!