G-Speed Shuttle Won't Power Off!

Just purchased a G-SPEED Shuttle TB3 4-Bay 16TB drive. I have it connected to a 5K iMac running High Sierra via an Apple TB2 converter. I can dismount the drive, but the unit will not power down when pressing the power button. Short of unplugging the TB or power, how can I power the drive off?

You press and hold for ~4 seconds and it will start the power down sequence.

These types of devices are designed to be on at all times though and aren’t required to be powered down.

I need to power it down to remove the drives. Unplugged the Thunderbolt cable and tried pressing the power button with no result.