Hi I had the issue for a while too. I discovered that depending on your environment, where you keep your miners that if you disconnect all your cables.
pop out the control board, flip it over you may notice some oxidization between the solder points on your board. It looks all white and powdery.
I grabbed a new firm bristle toothbrush and scrubbed it out. If it is there, it creates artificial jumps between circuits and the machine does not recognize the hash board.
BOOBmain, told me the same this as you, dead hash board. Once i cleaned the gunk out she purred like a kitten.
Hope this helps. I do take donis at:
e2c06e130e77a7c55a5697a762128f270be9bacad791590520c481ba225723143c63b929115f
If this fixes your prob.
