Cause

The cable length value 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) function. 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 Length field.

Click [OK] then start a new project check.