ERR_ADDRESS_UNREACHABLE
is usually due to the IP address of the miner changing (happens to me as well) so you gotta do as what keaton says, the SD reset method is really easy to do.
1, unhook your hasboards and disconnect their power plugs
2, remove control board from it’s housing, find SD port
3, insert said SD into the port (with THE UNIT OFF)
4, power on and hold the reset button (the shorter button with RESET in front of it)
5, let it do a full boot (leave alone for 5 minutes or until AFTER the lights stop flashing)
6, unplug to powerdown after the previous step has been completed
7, start hooking up a hasboard (preferably one by one in my experience to confirm the control board is functional) and power up and login to the web GUI/hiveOS to verify it’s working and connect other boards
8, set up your pools/wallets/overclocks
9, happy hashing!