Rick,
Thanks for your reply. I verified that all channels are on as your suggested.
The attached picture shows the button I want to use to turn on or off channels when using a preview. It does work for one sequence I created and it does not for others using the same profile.
As a test I created a brand new profile and sequence to verify if the button would work. The issue still exists, which lead me to believe that something got corrupted (or I messed up something).