Please check by doing the following:
Go to the windows control panel>Network and Sharing Center>click on the ethernet adapter that has the blue link listed>Click the "details" button>That will display the MAC address as well as the IP address that is assigned.
If not you may need to statically assign the IP to a range you can connect to the router on to be able to manage it.
To do that please:
Control panel>Network and Sharing Center>click on the ethernet adapter that has the blue link listed>Properties>Scroll down to IPV4>properties button>Set your address to the following:
DNS:set to use the same one from your ISP
and then hit ok to close all dialogs and then try connecting to the router to perform the management task.
If that is all correct and it still is not connected you may need to do a hardware reset. You should find a little reset button somewhere near the power... sometimes you may need a pin to be able to press it. Perform the reset according to the manufacturer.
Another simple explanation could be that the requester is attempting to connect to the router configuration page wirelessly. The Linksys firmware on many models has a feature that disables the adminstration page from the wireless network. Try connecting from a wired connection.
You have to reset your router. Press and hold the reset button for 30 seconds and try to configure your router again to resolve this problem. If this does not help, then you need to manually change the IP. This step requires and technical expert. Call 1-855-569-5945 and get 24/7 support from certified technicians.