Steps that I have done to get back the IP address on1 of S9 miner.
1.Switch off the unit by switching off the PSU.
2.Wait a few seconds,and with left hand ready to press IP report pushbutton,and wuth right hand ready to switch on the PSU.When ready simultaneously press the button for not less than 5 sec and PSU switch on.
3.Run any IP scan program.In my case I use Angry IP scanner.
4.Copy/  paste IP address to any browser.