I have an S9 whose 3rd chain GH/S(RT) is showing all zeros when it should be 4,500.88
I have rebooted & updated firmware but no change.
Any ideas?
Almost certainly you have a dead hashboard. You can switch signal cables (for example 1 to 3 and 3 to 1) to rule out malfunction on control board. If the problem moves to different slot you'll know it's the hashboard.
Unfortunately for warranty repair you need to ship the entire miner to Bitmain, if you still are under warranty period.