Easiest way to correct this is connect it to your router (since you have connectivity when it's going through the router) and look in the manual to find how you print out a sheet with the printer specs. This sheet will have the current IP address on it. YOu can enter that IP address into your web browser to access the printer GUI. At that point you can reassign the IP address to a network that's on the same subnet as your computers (that way you won't need the router in the middle for connectivity).
Hope this helps!