Generating midi, must unselect before it works

I have a script that generates some midi by inserting midi notes in to an item. What is strange is that I have to deselect the midi notes before they work. It's as if reaper is not playing them back until I move the cursor or interact with it somehow. The notes are inserted and everything looks to be playing, but it isn't(no midi notes are showing in the vol meter).

I guess I have to call some function in inform reaper of the changes?

Generating midi, must unselect before it works