The USB device might not be formatted in a supported format.
The OPUS-QUAD supports FAT16, FAT32, exFAT, and HFS+.
Please use one of the above formats.
Note:
* NTFS is not supported.
* When updating the unit's firmware, use a USB storage device formatted in FAT or FAT32.
The following may also be the cause of the problem.
・If you're using HDDs that consume more power than the USB port can provide.
■ If you're using a Mac
・ The OPUS-QUAD doesn't support the GUID Partition Map Mac OS standard format.
・ USB devices formatted with Mac Extended format (case-sensitive) might not be recognized correctly.