Hi winnielinnie & etorix,
When I unscrewed the mobo to swap usb flash drives, I didn’t notice that the back plane has a pcie kind of plug in to the mobo, since I was detaching the mobo from the bottom. (I did have a thought initially: wow, there’s hardly any connections from the mobo to the chassis–there was only a 4 strand power cable!)
Eureka! So this time, when re-attaching the mobo to the chassis, I carefully watched and made sure the pcie slot went into the mobo, and when I plugged it in, I got 4 lights on the front unit, and 4 drives working fine!
Thanks for helping 