R730 no fans turn on - entire cooling assembly gone?

(can this thread be moved to the PowerEdge forum? I couldn’t post there for some reason.) 

After reconnecting the backplane signal 1 connector, I reattached the cooling assembly. Now none of the fans work - 0 RPM, I tried resetting iDRAC and NVRAM. They are secured tightly- I even tried connecting individual fans directly to the motherboard.

What could have happened? How do I resolve this? The assembly has no electronic components, and the individual fans are fine.