I generally don't water my pumpkin plants, and they do fine. Twice a day is definitely too much. It's suggested an inch of water or rain a week. If it's particularly dry or hot I may water 2x a week. Raised beds may need a bit more. You could be rotting off the plants, and encouraging slugs with too much water.
Pumpkins will root along the stems so they will get water from more than just the original base of the plant and they are good at surviving without a lot of water in my experiences.
