Q.pruning grapevines
I have a well-established grapevine that produces a tremendous amount of grapes. Last November we had a freezing event before getting the usual amount of rains and I believe this combination hurt the grapevine this spring. This spring we have had a particular dry and warm, then wet and warm. My grapevine at this time is full of foliage and very tiny grape clusters. This year, however, I do not have foliage except on the bottom 2 feet for so. What should I do to encourage its return to is former glory? I have asked one neighbor about hers and she has the same situation.

Last winter was very harsh across the country. You are not alone is seeing the effects of this on your plants and gardens.
Me included!
Keep an eye on insects and disease on your stressed grapevine.
Pruning with most likely help rejuvenate your vine but you will want to wait to do so until it's dormant.
I have listed a few articles for you.
https://www.gardeningknowhow.com/edible/fruits/grapes/prune-grape-vine.htm
https://www.gardeningknowhow.com/edible/fruits/grapes/treating-grapevine-problems.htm
https://www.gardeningknowhow.com/edible/fruits/grapes/grape-vine-winter-care.htm