I can't reach 10.0.1.1 in my webbrowser

I see my Airport TimeCapsule in the Airport Configuration where the LAN-IP-adres is 10.0.1.1 I WAS able to reacht 10.0.1.1 in my webbrowser (Chome as well as Safari as well as IE) to manage the router. Now it's not possible anymore. get a message as " unable to connect" or similar.

When I use my IPhone I can get "into the router"

What can be wrong ???

Cheers

Han Colen