Others are shaped so that pollen must be carried from stamen to pistil by an outside agent. This is true, whether they are selfed or crossed. The outside agent is usually a bee, though flies, butterflies and other insects can also accomplish some of this. If your pots are indoors, you have excluded bees. Even if outdoors, they may not make a large enough number of flowers to attract the attention of the bees.
Bees are creatures of habit, and tend to work flowers in groups.
Try some hand pollination and see if the plant responds. I'll bet it does, and then you will have a conclusive answer to your question.