That would have a higher probability if the miner was recently moved/shipped, but when the hash rate suddenly drops (like how OP reported) then 90% change the board is dead and there is nothing that can be done about it, at least not as far as switching cables and whatnot, but of course, it's always worth the try.

Another thing that can cause this issue is a bad PSU, sometimes the PSU just can't handle 3 hash boards, an easy to troubleshoot both the wiring and the PSU in the same step would be to disconnect 1 working boards wires (PSU + data ribbon cables) and attaching them to the bad board.

If that fails, you might get lucky with custom firmware, use high voltage and low frequency, if the board shows up, then slowly increased frequency and decrease voltage until you get to the point where the board goes missing again.

If all of the above fails, simply disconnect the cables from the bad hash board and leave it inside the miner.