In short: only some USB 3 powered hubs can be directly linked to rasp pi (Superbpag is one such known example where it works; USB 2 powered Plugable also works directly with pi, not sure it it is enough for 2pacs).
most USB 3 hubs would not work by themselves (it includes Anker), however, don't despair, there is a simple runaround: use non-powered simple usb hub (like USB2 Sabrent for around $6), connect it to rasp pi, then connect your powered hub to Sabrent, then it should work, providing that you push the button on Sabrent to activate the slot (it should shine blue).
TL;DR either return your USB 3 hub (non-Superbpag) and get Superbpag OR get a non-powered hub like Sabrent and use it as a bridge.
Thanks for this. My USB 3.0 powered hub is made by Anker. As described, it does not work on my Raspberry Pi for most (but not all) devices. I followed your advice and bought a simple (non-powered) USB 2.0 hub and connected it in-line between the RASPI and the USB 3.0 hub. Unfortunately, I'm getting the same result. When I plug the 2PAC into the USB 3.0 hub, cgminer still cannot see it.
At this point, it looks like I'm returning the 3.0 and 2.0 hubs and will try to find a good 2.0 powered hub (but they are hard to find!).
my setup is sticks in Superbpag USB 3 powered hub, then Sabrent usb2 bridge, then pi. Many people use a setup like this.
This is guaranteed to work.