Mac Pro 5,2 problem with HGST 10TB drives

[macpro52]

I just bought 4 HGST Ultrastar He10 HUH721010ALE600 10 TB drives
and none are recognized internally on my Mac Pro 5,2. All were recognized and erased with an external drive dock. https://www.amazon.com/gp/product/B01E80N2E8/ref=oh_aui_detailpage_o06_s00?ie=UTF8&psc=1 Any idea what the problem might be? Not supported?

 

[jbarley]

Did you partition and format them for OS X while still mounted in the Dock after you erased them?

BTW hang on to that Mac Pro 5,2, it's very rare and might be very valuable someday.

 

[Draeconis]

Silly question, but were they actually connected to the SATA backplane?

Drives this large apparently have screw mounts in different places, which might have positioned the disk too far back to connect.