Q.Why have my sugar snap peas put out so much foliage, but hardly any peas?
Vines are 4-6 feet tall, tied loosely to a trellis. I have not used any fertilizer on them. It appears they are missing a nutrient or something. I also have a honey-bee hive in the area, so pollination should not be an issue. There are actually very few flowers on these vines; what can the problem be?

Certified GKH Gardening Expert
Since you haven't fertilized them, and they aren't producing well, I suggest having your soil tested. That will show what nutrients are lacking. You must have plenty of nitrogen since you get plenty of foliage. In the meantime, work in some well rotted compost to enrich the soil if you haven't already.
https://www.gardeningknowhow.com/edible/vegetables/peas/growing-snap-peas.htm
https://www.gardeningknowhow.com/edible/vegetables/peas/how-to-grow-sugar-ann-peas.htm