The needed configuration for the Internet connection can NOT be done via the Quick Setup. You need to exit or end the Quick Setup in order to proceed with the configuration.
On the menu left go to Network → WAN
and configure the following:
Apply the setting with Save.
If you have lost your username or password you can reset your account.
The router should now connect to the network by click on Connect.
The status Connected should appear and the Internet IP Address should NOT be „0.0.0.0“ anymore.
If there are problems to establish a connection check the above settings, especially Username, Password and Server IP Address/Name again.
On the devices connected to the wifi router, a dial-in using the Internet login is NOT NEEDED anymore. The wifi router will establish a connection automatically if one of the connected devices tries to connect to the Internet.