Pogoplug v4 only boots from USB hub

[nlcrj]

I have a Pogoplug v4 that has been running well booting from a thumb drive and using a 2TB HDD for use as a low power media server. I am in the process of migrating to a 1TB drive for media and Arch on the same drive and it does boot so far, but only when plugged into a USB hub. There are no other devices on the hub, and I can SSH into it just fine. If I try to plug the drive into the pogo directly, I just get the blinking green light and it doesn't boot. I'm fairly new to Archlinux so I'm kind of lost here. I would like to run this without a hub if possible.

Does anyone have any ideas why this isn't working?