Cause

No part number has been specified for the main function of the device or the main terminal of a terminal area.

Solution

1. Use the Go to functionalities to locate the device / main terminal in the project.
2. Open the properties for the main function of the device or the main terminal and bring the Parts tab to the front.
3. In the Part number / number of units / quantity table, select an empty field and click [...] in the Part number column.
4. The Part selection dialog opens. Select the part required.
5. If necessary, repeat this process for other parts that you want to assign to the main function / main terminal, then exit part selection by clicking [OK].
6. Close the property dialog by clicking [OK].
7. If required, start a new check run.