Cause

The number of connections is not specified for the cable's main function.

Solution

Locate the cable's main function in the schematic from the Message management dialog using the Go to (graphic) functionality. Then double-click the selected cable definition line and call up the Properties <...> dialog for the cable. If not already set by default, switch to the Cable tab and enter a value in the Number of connections field. Alternatively you can carry out a part selection and assign a suitable type to the cable. To do this, click [...] beside the Type field and select the cable with the required properties from the part selection dialog.

Click [OK] then start a new check run.