B..
Anything in the squash, cucumber, or gourd family, is NOT a companion plant with potatoes. The same with tomatoes, peppers, and eggplants. How long ago did you plant? pumpkins need 90-120 days until maturity. How big are your beds? Pumpkins need space. They also need very, very deep watering. If they are crammed in a tiny space and not watered deeply and thoroughly, they will be very parched. Are you fertilizing? Pumpkins need a neutral soil PH, and lots of good organic fertilizer. Do the plants have a white film, are they yellow and splotchy? If you are watering from above, directly on the leaves...they will mold. You have to water pumpkins from below, underneath the leaves.
The biggest culprit with pumpkins not fruiting, is under-pollination and an unhealthy plant. Healthy plants, fruit. Flowering does not mean the plant is healthy, fruiting does. Make sure they are getting a lot of deep watering, and only water when the soil is dry. Water from below. Plant flowers that bees like, and take out all the potatoes. If you are trying to grow pumpkins in a small space, they don't have much chance. They need to be spread out, and the require so much deep water. If all the plants in a little space are fighting for water, they won't fruit much. Pumpkins are VERY prolific. Since you've only grow about a dozen pumpkins a year, I think you really don't have the optimal space. You should be getting more then that.