Based on what you have already tried out, the only thing you have left is to try to replace the 18-pin data cable that connects the controller board to the affected hashboard.
https://imgur.com/a/97bD1Gs
If you don't have a spare one (I recommend always having, just in case) you can turn off the miner, disconnect the PSU and swap one of the working ones from the other two boards into the affected one to check if it's alive. If after doing so the board still doesn't work that probably means it's dead and you will have to replace the whole hashboard for a new one
https://imgur.com/a/97bD1Gs
If you don't have a spare one (I recommend always having, just in case) you can turn off the miner, disconnect the PSU and swap one of the working ones from the other two boards into the affected one to check if it's alive. If after doing so the board still doesn't work that probably means it's dead and you will have to replace the whole hashboard for a new one
Before assuming this, test. Simple: disconnect all the other boards and swap cables.
Test each board one by one, and swap data cables one by one, and power cables one by one on all three boards while single connected. Then you will know for sure if the data cable is the culprit. Takes time, but gives you the right answer instead of wild guessing.