You have specified that sloped pipe be drawn, but are trying to connect to an element that doesn't support sloping connections.

public static FailureDefinitionId AttemptToConnectNonSlopingElementToSlopedPipeWarning { get; }

Public Shared ReadOnly Property AttemptToConnectNonSlopingElementToSlopedPipeWarning As FailureDefinitionId
	Get

public:
static property FailureDefinitionId^ AttemptToConnectNonSlopingElementToSlopedPipeWarning {
	FailureDefinitionId^ get ();
}