No USB3 hub on RT-AC56U

I am unable to use a USB 3.0 hub on my RT-AC56U. I have multiple Sabrent USB 3.0 dual docking stations that I am trying to attach to my RT-AC56U. I have tried the 7 port Anker and the Insignia 4 port USB 3.0 hubs. If I attach the docking stations directly to the USB 3.0 port on the router the drives come up fine. Once I put the hubs in I get nothing at all. Here is the strange part. If I plug my old 7 port USB 2.0 hub in and attach my docking stations all the drives come up fine.

So why...

No USB3 hub on RT-AC56U