No internet connection

Hello,

I subscribed to TMobile Thuis and could successfully activated it a few days ago, but recently it stops working. When I am trying to connect to WiFi, the HG659 router says that there is no Internet connection.

I tried to restarted it, moreover I reset it but it didn't help me. The WAN light is on and not blinking, WiFi light is also on, but Internet light is off.

Please, advise me what to do next?

Thanks,
Yuri.