I have not done this, so what I am suggesting is not tested, and it could be mistaken. Looking at the admin guide and my OBi202 web pages lead me to believe that I have it right. I suspect that your power loss was enough to reboot the OBi but not to reboot the computer. Maybe the computer is on a UPS, and the OBi202 not. Anyway, the plan is to always have the OBi202 to always assign the same IP address to the computer each time it asks for an IP address.
The following is accessed from the local web page on your OBi202. Go to Status>Lan Status and record the Client and the MAC address for the computer.
Then go to Router Configuration > DHCP Reservation
Create an entry for the computer. I suspect that you could enter either the ClientName or the ClientMACAddress, but maybe it wants both. Enter the part of the IP address into the box. If using the default IP addresses suggest picking something like 192.168.10.40, which would put it outside of the range that the router assigns things that are not in the reservation list, but still within the subnet.
You could do this for each device, or it might only be important for the computer.
Please comment on the router operation, because there have not been many posts reporting on that.