Sonar Platinum
I insert a simple instrument track for Additive Drums 2 , choose a beat and drag it to the newly created track.  So far so good, I have an 8 bar clip pasted in the track.  When I expand the track I would expect the data in the clip to be reproduced in the expanded clip but that does not occur.  Instead it just expands the clip with no data (silence).  I still have the 8 bars of drums and then nothing.  Am I missing something?
 
Thanks!

right-click on the clip then select Groove-clip looping

After pasting the clip in the track, convert it to a groove clip (keyboard shortcut CTRL+L), then click-drag the edge of the clip for as long as needed.