Rule #1: Check your loop.

It could be that the yellow loop locators are active and set either to a very short range or not the full track. When the loop locators are active, the studio will only publish and export the clips within the locators. If they're set too short, there may not be anything to export at all.

A solution is to turn off the loop locators by clicking the yellow line in the timeline or ticking off "Loop" in the transport bar. 
You can also set the loop locators to your song from start to end so you can decide the range you'd like to export.