That USB is probably a power port, not an output.
Make sure the stick is actually getting power. I’m guessing it’s trying to draw power from the HDMI port but can only get enough initial power to start and then is turned off.
Wondering if the problem is this xiaomi device is powered from the HDMI port or a USB port? If so you should check if your AVR supports power over HDMI. If not, then use an AC adapter or buy a device like the Shield that uses an external AC plug.