Try connecting that zero hashrate hash board in chain 7 (connector J7 in the controller) to another controller data connector.
Try to see if there is red LED light on in the hash board.
If the light is off and changing controller data connector makes no difference, and power connections etc. are ok, then you have a dead hash board and it is time for a repair job.
Warranty repair if you still have warranty left or paid repair if there is no warranty time left.
Bitmain has this guide for broken hardware:
https://enshop.bitmain.com/workOrderGuide.htm
