Cause

Several interconnected bus ports are combined into a physical network. In the concrete case no name was assigned to the physical network.

Solution

1. Locate the network via the Go to (graphic) functionality, that is offered to you by the popup menu of the Message management dialog, to jump to the first network / bus cable connection point.
2. Call up the property dialog of the network / bus cable connection point and enter a value in the Bus data tab in the Physical network: Name field. Alternatively to this you can also enter the name into another network / bus cable connection point that is connected to the physical network. It is sufficient if the name of the physical network is entered at least in one of the network / bus cable connection points that are interconnected.
3. Then start a new check run.