2019.40.50.7 and mine stopped working (camera icon no longer shows up) a few days ago as well. I have two high endurance SD cards that I swap into the adapter when I take one inside to dump. Neither work. Other random USB drives do work. A reboot did make it show up briefly, but it went away again. Rebooted it a few times.
Thing works fine in computer. SD cards both work fine via the usb adapter or directly in a computer. They were originally ext4 but I've tried reformatted as fat32 with no luck. Tried both USB ports in the car. The unit doesn't heat up too much in the car (but will heat up a lot if I plug it into a USB3 port in a PC!)
It does still heat up a bit when plugged in, despite the camera icon not showing up... so electrically it's doing something. Wish I had easy access to the system logs to see what it's whining about :(
edit: https://www.amazon.com/dp/B01EFPX9XA grabbed one of these and works again, same SD cards :\ My kingdom for an error message.
Maybe it's overheating? I personally do not recommend that style of USB readers due to the MicroSD card being close to the front USB ports, which are notorious for being very hot.
I've always recommended something with the reader away, such as https://www.amazon.com/dp/B01EFPX9XA
I have always recommended this combo (paired with a High Endurance MicroSD).
However, if Tesla continues its development to allow more video streams to dump to the USB drive (currently there are *4* video streams being written), I'm most likely going to change my recommendation to a USB SSD, ex: