FRITZ!Box 6840 LTE Service - Knowledge Base

FRITZ!Box 6840 LTE Service

Cannot update FRITZ!OS: Error message after selecting a FRITZ!OS file

The FRITZ!OS update for the FRITZ!Box cannot be installed. After you select the FRITZ!OS file in the FRITZ!Box user interface, one of the following error messages is displayed:

  • "The update failed: The specified file does not contain any valid firmware for your device."
  • "FRITZ!OS Update failed. An unspecified error occurred during the update."


  • The downloaded FRITZ!OS file is not suitable for your FRITZ!Box, for example it is for a different FRITZ!Box model, or the file may not have been downloaded completely.

Important:Some of the settings described here are only displayed if the advanced view is enabled in the user interface.

1 Downloading the FRITZ!OS file again

  1. Call up in your web browser.
  2. Switch to the folder for your FRITZ!Box model, then to the subfolder "firmware", and then to the folder named "english".

    Note:The complete model name of your FRITZ!Box is displayed in the FRITZ!Box user interface on the "Overview" page and on the underside of the device.

  3. Download the latest FRITZ!OS version for your FRITZ!Box with the file extension ".image" to the computer.

2 Clearing Internet connection and closing all active programs

  1. Remove the SIM card from the card slot on your FRITZ!Box to clear the Internet connection.
  2. Close all active programs running in the background on your computer such as virus scanners, firewalls, etc.

    ATTENTION!Only disable firewalls when updating FRITZ!OS and re-enable them before establishing an Internet connection. This software protects your computer from attacks from the Internet and prevents other threats (for example computer viruses) from being executed.

3 Restarting the FRITZ!Box

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

4 Updating the firmware manually

  1. Click "System" in the FRITZ!Box user interface.
  2. Click "Update" or "Firmware Update" in the "System" menu.
  3. Click on the "FRITZ!OS File" or "Firmware File" tab.
  4. Click "Save Settings".

    Note:Save your FRITZ!Box settings again under "System > Backup" right after successfully completing the installation. Then you can always restore it to a working configuration.

  5. Click the "Browse..." or "Choose File" button.
  6. Select the FRITZ!OS file that you downloaded (image file) and click the "Open" button.
  7. Click the "Start Update" button.

The "Info" LED flashes while the update is being transmitted to the repeater.

5 Establishing an Internet connection

  • Reinsert the SIM card into the slot.