Can't see inserted drives

I have a used PowerEdge T630 with the backplane plugged into the SW-RAID ports on the motherboard.  There is no formal RAID card installed.

I have 2 SATA drives and 6 SAS drives plugged into the backplane.  I can see the SATA drives but not the SAS drives. I've removed the SATA drives but still cant see the SAS drives.  I know the SAS drives work because they were removed from a working system.  The SATA drive lights behave as expected, but the SAS drive lights just flash on and off.

Backplane DP/N: 070YDP

Cable DP/N: 04G20M

I do not need RAID at the Boot/BIOS level as I plan to use ZFS in ProxMox, but I need to be able to see all the drives in order to use them.  What am I missing in order to see and use all of the drives?