If you see this error message
This means that the companies company card that you are using for download wasn't locked in to the tachograph.
If you see this addition warning message:
This means that there wasn't any company ard locked in to the tachograph.
You probably will be able to download the tachograph files but the company can get a fine because the company card wasn't locked in.
You have to insert the companies company card in the tachograph and when you remove it from the tachograph you have to answer no to the question if you want to unlock the company card from the tachograph.
If there is another company card locked in to the tachograph you will see this error messages: Another company card locked in