My E-750 stopped sharing files via USB yesterday. I can see only directory /mnt/sda1 (microsd) on the GUI and Luci. On the DLNA server options there is a /mnt on directory menu, but only sda1 is visible.
Noticed before that both USB stick and the router getting hot during the streaming. Tried to factory reset and changing the firmware but no luck so far. E-750 is not detecting anything plugged in the USB port.
So when you plug USB device to the USB port, can you check the system log and kernel log to see if there is anything?
If no log then it seems the USB is damaged.
It looks like it’s dead, could find any logs after insertion.