You have to make certain that the Radius Elbow is part of the button mapping for the service you are in.

1.  Is the radius Elbow a button on the service?

2.  Does the Radius Elbow have a Button Code on the button?  (Right click the button, & choose button properties)

3.  Is this Button Code in the button mapping for a Bend in this service? (Click on the service hyperlink, choose the second tab from the left "Button Mappings", make sure the Button Code from #2 is in the "Alternate Codes" column for a Bend, if not, add it.  (Note, it may be there, but the button code box is unchecked)...if this is the case, check it.)