Onkyo TX-RZ3100 User Manual page 148

Troubleshooting
USB storage device
USB storage device is not displayed
Check whether the USB storage device or USB cable is correctly inserted to
the USB port of the unit.
Disconnect the USB storage device from the unit, and then try reconnecting.
Performance of the hard disk that receive power from the USB port of the unit
is not guaranteed.
Depending on the type of format, the playback may not be performed normally.
Check the type of the file formats that is supported.
USB storage devices with security functions may not be played.