try hard restart from the psu or power strip power on/off, then wait 15-20 min, then see if you have connection to gui.
also do what @gt said-check the IP of the miner (is it on default DHCP or manual?)
you don't need to do anything with ssh yet, just direct gui access via ip address
if after 30min not hashing and you have older s9 (non-autotuning), then try to roll the July firmware back in.
Best would be to contact support@ anyway.