Mz32ar0 top slot nonfunctional

Gigabyte Mz32-ar0, epyc 7532, latest fw/bios/bmc. Using 16x 32gb 2666mhz ecc ram

power cycled repeatedly, replaced both the cpu and motherboard separately (seller has been great). Cpu torqued and retorqued with both the old and new cpu/mb combo. Everything mostly stock in mobo settings except for virtualization and above 4g. Slot tested using perfectly functional 9400-16i that I am using in the second to top slot. All slots set to auto. Tried the top slot with x8 mode to see if that would make the 9400 work there, and it did not. On the block diagram I see that this slot is shared with the slimsas 4i connectors above, but I am not using those or the mezz slot. Any help would be… helpful. Lol.