Fan is running when I plug it in.
I have a set still working, so swapped the cables and the power brick, the working one still works. The not working one is still not detectable and no light when connected to usb.
After a month of smooth mining, I had one of four the light wasn't on.
Unplugged it and plugged back in, light came on.
Found, by checking device mananger, that windows assigned it usb port 7 instead of 5, which was the port to scan in my bat file.
at first, I changed the bat file, then during one of maintenance sessions I
Shutdown. rebooted and the usb port went back to 5.
Anyway its worth checking that all your config is as original.