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FRITZ!Box reports "Username already used"

It is not possible to delete entries for IP telephones, for example FRITZ!App Fon, from the list of telephony devices. When you try to, the following error message is displayed:

"An error occurred. Error description: Username already used. Please enter your data again. If the error occurs again, please consult AVM Support."

Cause

  • The FRITZ!Box's telephony settings are inconsistent.

1 Saving settings

  1. Click "System" in the FRITZ!Box user interface.
  2. Click "Backup" in the "System" menu.
  3. Click on the "Save" tab.
  4. Enter a password.
  5. Click "Save" and on the FRITZ!Box, confirm that the procedure may be executed if asked to do so.
  6. Save the file "FRITZ.Box[...].export" on your computer.

2 Loading the factory settings

  1. Click "System" in the FRITZ!Box user interface.
  2. Click "Backup" in the "System" menu.
  3. Click on the "Factory Settings" tab.
  4. Click the "Load Factory Settings" button.

3 Restoring settings

Now you can restore all of the settings except for the telephony settings. Afterwards, you must manually reconfigure the telephony functions:

  1. Click "System" in the FRITZ!Box user interface.
  2. Click "Backup" in the "System" menu.
  3. Click on the "Restore" tab.
  4. Click the "Browse..." or "Choose File" button.
  5. Select the file "FRITZ.Box[...].export" with the settings you want to restore.
  6. Enter the password you entered when saving the file.
  7. Enable the option "Select manually the settings to be restored".
  8. Click the "Restore" button and on the FRITZ!Box, confirm that the procedure may be executed if asked to do so.
  9. Enable the option "Select all settings".
  10. Disable the option "Overwrite all telephone numbers and telephony settings".
  11. Click "Apply".