Cause

The required value is missing at the Start address of PLC card properties at a PLC box that only has inputs or outputs. In the case of a PLC box that disposes of inputs and outputs, the required value is missing at the properties Start address of PLC card and / or the Start address 2 of PLC card.

Solution

1. Locate the PLC box in the schematic using the Go to (graphic) functionality that is provided by the popup menu of the Message management dialog.
2. Open the property dialog of the PLC box.
3. Bring the first tab to the front.
4. In the properties table fill in the value fields of the properties Start address of PLC card for inputs and Start address 2 of PLC card for outputs in accordance with the conditions described above under 'Cause'.
   
5. Click [OK].
6. If required, start a new check run.