Hi Val,
You do not need to try and pollinate the flowers. They are self pollinating. Tomatoes are also. Cucumbers, squash, and melons need to be pollinated by insects or hand.
Two factors that could hinder the development of fruit are too high of temps or not enough water. But sometimes I notice the first set of flowers on plants don't develop fruits/seeds when really nothing is wrong. The subsequent flowers produce without problems. I'm not sure why.
Remy