Velocity problems

As a recent convert to Platinum from 8.5, I am still learning the new interface and am sure I am probably causing the problem described below.
During the sequencing process, changing velocity on some of my midi tracks quits working. Other tracks work fine. On the track that quits working, you can see the velocity in the controller pane and can increase or decrease it, but no change in dynamics is heard even though it visually shows that it was changed in the controller pane. It's almost like I have locked the velocity for that track in some way. 
Again, I'm sure it is probably operater error, but any suggestions would be appreciated. I'm clueless!
Thanks