MarketPress not charging shipping when using "Calculated Options" setting

I've started using the new Calculated Options setting in MarketPress, and the first transaction did not charge shipping for the product. A few settings for reference:

- Inventory is de-selected because this product is drop shipping from the publisher
- No special shipping cost is entered
- A product weight was not entered when the transaction occurred that applied no shipping cost (I have since added a weight)

Please let me know if you have an idea why no shipping is being applied. Thanks!