Ok so you discovered the condition 'On Consume Purchase Completed' doesn't trigger? Same for me.
I found the action to consume a product DOES work (eg: 'Consume Product: StarPack1 x 1' should be ok I think).
Would it work for your game if you moved the actions from under 'On Consume Purchase Completed' and repositioned them after the consume action?
So your code for purchase would look something like:
Is Product "StarPack1" purchased (yes)
>Consume product: "StarPack1"
>Set Purchase to ""
>Add 400 to Stars
>Set item "Stars" to Stars
Not sure if this helpful..