I've identified the issue. When I was setting the sales regions, I didn’t select all 175 countries. However, I set the availableInNewTerritories attribute to true. As a result, I wasn't allowed to submit for review. If all 175 countries are selected for sale and availableInNewTerritories is set to true, submission for review is allowed. But if fewer than 175 countries are selected, the availableInNewTerritories attribute should be set to false in order to submit for review.