@MrVegas76 

Hi,

If I am not mistaken, Deutsche Telekom always requires the Internet connection to be established via PPPoE, no matter whether it's their DSL broadband or fiber broadband.

I would try PPPoE with Internet VLAN ID 7 instead of Dynamic IP.

  @woozle I tried that, but the router wants to have the name and password.
And I don't have that, I took my login details from the homepage, but without success.

  @MrVegas76 

The username should be a combination of Anschlusskennung, Zugangsnummer, Mitbenutzernummer and @t-online<dot>de

The password you need is called "Persönliches Kennwort".

https://www.telekom<dot>de/hilfe/vertrag-rechnung/meine-telekom/kundencenter/internet-zugangsdaten   (replace <dot> with . )

  @woozle Thanks for your support, but unfortunately that doesn't work either

  @MrVegas76 

See if you can get a clue be looking at the System Log of the GE800.

1) In the webGUI go to Advanced -> System -> System Log and then click "Clear All" to remove all existing log entries.
2) Go to Advanced -> Internet and click "CONNECT" to initiate the PPPoE connection again.
3) Go back to Advanced -> System -> System Log and read through the newly added messages. Look if you can spot something that obviously doesn't seem right.