Cause

No plug designation is assigned at a PLC connection point or a bus port.

Solution

1. Locate the PLC connection point or bus port in the schematic using the Go to (graphic) function from the popup menu in the Message management dialog.
2. Open the property dialog of the PLC connection point or of the bus port.
3. Bring the first tab to the front.
4. Enter the missing value in the Plug designation field.
5. Click [OK].
6. Then start a new check run.