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The lack of pollen could be a result of not enough sun (pumpkin plants need 6-8 hours of sun) or inconsistent watering. It could also be a result of extremely high temperatures for multiple days in a row. Additionally, if your nighttime temperatures are averaging as high as the low 70's F., that will affect pollen viability as well. There is nothing you can really do about the lack of pollen except perhaps try to find someone locally who may have a healthy plant and beg them for a few of their male flowers. You could transport those flowers back to your plants and try shaking or wiping the pollen off onto the female flowers at the appropriate time of day (before about 10:00 a.m. local time).

Here are some additional articles that may help you with future pumpkin plants:

https://agdev.anr.udel.edu/weeklycropupdate/?p=1583

https://extension.psu.edu/plants/sustainable/documents/Pumpkin%20Pollinators.pdf

Read more at Gardening Know How: Pumpkin Plant Not Producing: Why A Pumpkin Plant Flowers But No Fruit https://www.gardeningknowhow.com/edible/vegetables/pumpkin/pumpkin-flowers-but-no-fruit.htm

Giant Pumpkins do not like extremes, cold or heat.

This link may have some suggestions for you.

http://www.maine.gov/dacf/pumpkincam/how-to-grow-pumpkins.shtml

I do know that a Pumpkin Farmer friend of mine creates tents above his Giant's. This creates shade but still air circulation for his big beauties.

I'm sorry your pumpkins aren't producing for you!

Stress, a calcium deficiency, even lack of pollination (even though you have seen bees) could all be contributing factors to your pumpkin blooms falling off.

There are handful of things you can do to remedy all of these. This article may help you:

https://www.gardeningknowhow.com/edible/vegetables/pumpkin/pumpkin-fruit-drop.htm

Pumpkins are considered a relatively heat-tolerant plant, so your pumpkin can most likely make it if you give it a chance. If you can, provide some shade for the plant. Water consistently in the early morning, and avoid watering during the hot part of the day since this can "burn" the leaves. Also make sure you don't over-fertilize as this can cause crispy leaf edges.

Planting in hills certainly will help with water drainage, though this is ideal, many other conditions go into a healthy producing vine.

Adequate watering, full sunshine and pollination are also needed for your vines to produce.
Here are some links to help refresh you on the care requirements.

https://www.gardeningknowhow.com/edible/vegetables/pumpkin/pumpkin-growing-tips-for-halloween-pumpkins.htm
https://www.gardeningknowhow.com/edible/vegetables/pumpkin/pumpkin-flowers-but-no-fruit.htm
https://www.gardeningknowhow.com/edible/vegetables/pumpkin/hand-pollinate-pumpkins.htm

There could be a few issues with the pumpkins.
Flowering and lack of pollination may be a likely cause of no pumpkins forming.
You can try self pollinating by brushing the pollen from one flower to the next with a small brush.
Animals love to dine on pumpkin vines and pumpkins, but the damage you describe may be a Squash Borer.
Pumpkins need a lot of water to form.
Here are some links with more information and hopefully, fingers crossed a pumpkin may form.
I hope this helps for next years garden (don't give up!--if you it makes you feel any better--my 6 plants this year, I got 2 pumpkins!)
Hopefully a fun trip to a pumpkin patch this Fall can save the lack of pumpkins!

https://www.gardeningknowhow.com/edible/vegetables/pumpkin/pumpkin-growing-tips-for-halloween-pumpkins.htm
https://www.gardeningknowhow.com/edible/vegetables/pumpkin/pumpkin-growing.htm
https://www.gardeningknowhow.com/edible/vegetables/pumpkin/saving-pumpkin-seeds-how-to-store-pumpkin-seed-for-planting.htm
https://www.gardeningknowhow.com/edible/vegetables/squash/squash-pests-identifying-and-preventing-squash-vine-borer.htm