Sophos Anti-Virus for Windows: error 0x80040F04 after installation

Despite apparently successfully installing, Sophos Anti-Virus for Windows displays a white-cross on a red-circle by the Sophos shield icon in the system tray, and error number 0x80040F04 is found in the Sophos AutoUpdate trace log (inglés) (ALC-yyyymmdd-hhmmss.log).

This error is found when the server cannot be contacted, and Sophos Anti-Virus cannot update.

What to do

Check the following:

• did you use the correct username and password in your update details?
• does 'Everyone' have full permissions to the Central Installation Directory (CID) folder?
• are you using a proxy server?
• is your internet connection functioning correctly?