Maybe your laptop is not yet connected in your wifi...
How can i change my password?
check the physical connection from your router to your computer/laptop.. your computer/laptop's LAN LED should be blinking or at least lit.
try to logon again to your router's page. if you still encountering problem, try to restart your router or run command prompt (Window Key + R then type CMD).
on the command prompt type ipconfig | find "Gateway"
the default gateway that will appear is your router's ip...
try to access your router using that ip..