Cause

You have inserted at least two symbols into the schematic and connected them together. At a minimum of one connection point, two identical connection point directions (displayable as arrows in the graphical editor) have been placed on top of each other, so that one of them covers the other. It is also possible that you have placed two identical symbols (same variant) in such a manner that their insertion points lie directly above each other.

Solution

First, use the menu item View > Connection point direction in the graphical editor to display the connection point directions of all components. Use the Go to 1st coordinate popup menu item in the message management dialog to find the affected components in the schematic and check where connection point arrows in the same direction lie on top of each other. Move the components so that an autoconnect line is formed between the connection points. If the insertion points of identical components lie on top of each other, then move the symbols so that their connection points in the same direction cannot influence each other.

Refresh the connections and then start a new check run.