Are you using dynamic IP addressing? You should use static (manual), or if you have a DHCP server, you could have it reserved via mapping it with the MAC address; also try to release and renew the IP on the computer and see if it's using static.
Recently we have had a few power outages that reset the IP address. Over the weekend, we lost power again and we are unable to scan. The IP address on the machine matches the IP address on the computer. Any ideas how to fix it?