If you changed subscription from VDSL to Fiber, you can keep using your FRITZ!Box without any problem. However, the fiber configuration is slightly different. Below you will the guide of how to adapt the FRITZ!Box's configuration so it can work on a fiber line.
Step 1 — Opening the web interface
Open your web browser (Internet Explorer, Firefox,…) and go to the web interface of your FRITZ!Box. By default, it should be reachable via http://fritz.box or http://192.168.178.1.
Enter the password of your FRITZ!Box. You can find it on the white sticker on the underside of the device:
Step 2 — Configuration wizard
Choose Wizards in the left menu and click on Configuring the Internet Connection.
Follow the configuration steps, as explained in the guide How do I install and configure my FRITZ!Box 7530 (AX) for use with a fiber connection
Manual configuration
If your FRITZ!Box is not purchased at edpnet or if for some reason, the automatic configuration didn't work, try the manual configuration.
Choose Internet - Account information in the left menu.
Make sure that edpnet is still chosen as Internet service provider. Change the Type of Connection from edpnet VDSL to edpnet Fiber and fill in your username and password (sent after the activation) in Account information.
Click on Apply to save the settings.