The USB device you have plugged in is not supported by the HTS3544/37 or the HTS3555/37.
- Unplug the unit's AC power cord for 30 secs then plug it back in to reset the unit
- Download and update the set with the firmware update version 28
(Firmware update version 24 can be found by clicking on the model you have HTS3544/37/ HTS3555/37