Based on the error you are seeing, I would agree that something has gone wrong with either the PC settings for Ethernet communication, or with the ESS itself. I would suggest running the SCU (Smoothstepper Configuration Utility) again, which may be able to resolve the issue. You can find our instructions for this in the software setup guide on our site:
CNC Software Setup Guide | CNCRouterParts
If that doesn't resolve things, it would be good to see what the lights look like on the Smoothstepper in your system. It's possible something got corrupted on the ESS during the power failure, and that you will need to use a different utility to fix this. If that's the case, give us (or Warp9) a call and we can offer assistance with this.
Best regards,
Ahren
CNCRouterParts