Some individual software, while it is launched from within the user's session, it may elevate itself when running or run under the System user account. If this happens, the encryption keys will not be available to that software's process and access will be denied to the containers.
Example scenarios where the above behavior may be experienced are when software is running under a different user context within the users session. Magnus Box runs the backup as a service user account (usually "NT SERVICE\backup.delegate" or "LOCAL SYSTEM" in some cases). The DESlock virtual drive is unavailable for other user accounts on the system.
It's possible to mount a virtual disk globally so all users on the system will be able to access its contents. This is done using the [DESlock+] command line tool
Follow DESlock's own instructions to mount the drive for all users.