Sophos Anti-Virus: error 00000067 when attempting to update

Issue
There is a red circle with a white cross on the Sophos shield. When you open the Sophos AutoUpdate log (C:Program Files\Sophos\AutoUpdate\logs\ALUpdate<TimeStamp>.log) on the affected computer, you see the error:

The manifest file for [product] was invalid

If this is a managed computer, Enterprise Console may report the following error for the endpoint:

Code: 00000067
Description: Failed to install Sophos AutoUpdate: Package authentication failed

What to do

This issue indicates that you have not upgraded the security certificates on your endpoint computer. Please refer to Endpoint Security and Control: fixing endpoint computers that use outdated security certificates for more information.