Do you have another S5 to check if the BB is damaged or not. Also try with different PSU if you have one. How did you connect your S5 to the network? Also did you try to reset to factory default?
He already used another S5 to check if its the BB, and has swapped PSUs.
I have an Antminer S5 which is not working. It does not appear on my list of network devices and so it is inaccessible by HTTP or SSH.
When the Beagleboard and controller board are swapped with known good components from another S5, the miner works as expected. I've contacted Bitmain support and they've advised trying to re-image the Beaglebone board. The problem is I don't know how to do that, and I can't get a clear answer from Bitmain support on how to do it either.
How have you been in contact with Bitmain? I would advise asking to RMA the controller board as the solutions (even if they work), are rather painful.
In the future you can get S5 support
here or
here.