If you created an anchor by clicking (rather than click-dragging) the scene, the anchor does not have any tangents by default. However, you can add a pair of tangents manually.
  +  
 -click
               and select Anchor Presets from the Marking
                  Menu.
               Two options appear, Bezier and Bezier Corner.
You can also remove tangents to create sharp corners.
  +  
 -click
               and select Anchor Presets from the Marking
                  Menu.