Homebox 644 Internet connection problem

Hallo.

I have an issue with my homebox 6441 and I would like to ask for help.

Everything was OK with my homebox 6441 since Juny, but today I suddenly lost connection to the Internet. "Power", "WLAN", "DSL", "Internet" etc lights are green. 192.168.1.1 is accessible and according the "Aktuelle Geräteinformation" my online-status is "Verbunden". 

I have already tried to reset (via reset button and by turning it off/on) the homebox and I've checked wires but the Internet still not working. 

Maybe somebody knows how to solve this problem?

Thank you in advance.