i know you said you have re-imaged multiple times, but have you used the same image file each time? Maybe thats the issue. Try re-downloading the file and go from there if you havnt already.
Thanks AmDD I will try that. I am also buying some class 10 Sandisk 8gb cards to see if maybe I got a bad batch of NOOBS cards shipped with the Pi's...always a possibility. Not much more I can try if that doesn't do the trick.
Anyone else having this issue with the Controla software or can I pretty safely say that I am having some type of hardware issue? What is everyone using for USB hubs for 20 miners?