Cause

There exists a connection of the "3D mounting layout" representation type in a layout space whose corresponding multi-line connection does not exist in the schematic. The source and / or target of the multi-line connection has possibly been deleted from the schematic subsequently. But it is also possible that the source or the target of the connection has been moved in the schematic, thus preventing a connection in the form of an autoconnecting line between the source and target connection points.

Solution

1. Locate the connection of the "3D mounting layout" representation type in the layout space using the Go to (graphic) functionality from the popup menu in the Message management dialog.
2. Follow the connection in the layout space both up to the connected source and the connected target.
3. Highlight the source and target in each case.
4. Using the function Go to (counterpiece) from the popup menu, determine whether the source and / or target also exist as multi-line counterpieces in the schematic.
   
   If no jump to the multi-line counterpiece from the layout space is possible, then it is missing from the schematic.
5. Add to the schematic the missing source and / or the missing target with the corresponding parts data (device). Place the source and / or target in such a way that an autoconnecting line and thus a connection between the source and target connection points can be formed.
6. If required, start a new check run.