Alternatively: USB drive does not read.
I browsed google search reasults on the topic for a bit, and the majority of articles said “make sure its actually plugged in”, and “make sure you didn’t bend the usb drive in half because that would cause it to stop working.” Unfortunately the more words you use to describe a solution, the more popular google will make it. So most of the articles about the topic are just words around a solution, and the author were writers and not technologists – meaning, the writers write the words because its their job and you read them because you are the product being bought and sold by advertisers. Neither one of which activities actually addresses the issue. I’m afraid that even now, writing this article, I feel obliged to satisfy this “unwritten” social contract, to satisfy the requirement for length (and maybe keywords). Realistically, this paragraph is vacuous and there is no real reason for you to have read it.
In any case, my solution is plain and simple (and my hardware is excellent). Insert the USB drive and wait. You may need to wait a while – severall minutes. If the USB drive is formatted in FAT32, the filesystem is slow, maybe fragmented and poorly indexed. The projector may take around 5 minutes to make the USB drive visible. There is nothing wrong with the hardware, you just have to wait. There is no actual problem.
There you go – fixed!