I am trying to use a Connector in ER diagram. I drag two Entities on the page. I then drag a Connector to connect the two. I left-click on one end of the Connector and while holding down the left mouse button, I drag it over an Entity. The Entity box shows in red, indicating that the connection is established. However, when I release the mouse button, the Connector stays where it is; rather than changing to show that the Entity is connected. What am I doing wrong?