Cause

An unconnected symbol connection point was identified for a pin in the schematic. The message also appears if the pin has multiple symbol connection points, only one of which is connected to a component.

Solution

1. Locate the relevant pin in the schematic using the Go to (graphic) function from the popup menu in the Message management dialog.
2. Connect all open symbol connection points of the pin with a component so as to form autoconnecting lines.
3. Or, if the pin is no longer needed, delete it from the schematic.
4. Then start a new check run.