Sounds like lack of pollination. You could try hand pollinating, or just wait to see if conditions get better for pollination. On my eggplant, I had several flowers bloom and then die, but I now have loads of fruit growing.

Info from the below website:

What to do for eggplant blossoms drying out due to a lack of pollination:

An eggplant flower is normally wind pollinated, meaning it does not rely on insects like bees and moths to pollinate it. A pollination problem can occur when the weather conditions are very wet or very humid or are very hot. When the air is very humid, this causes the pollen eggplant flower to become very sticky and it cannot fall down onto the pistil to pollinate the flower. When the weather is very hot, the pollen becomes inactive because the plant thinks that it cannot support the stress of an additional fruit along with the hot weather. In a sense, the plant aborts the blossom so as not to stress itself further.

Eggplant flower hand pollination:

If you suspect your eggplant flowers fall off due to a lack off pollination, then you can use hand pollination. Eggplant flower hand pollination is easy to do. All you need to do is take a small, clean paintbrush and move this around the inside of the eggplant flower.

http://www.gardeningknowhow.com/edible/vegetables/eggplant/what-to-do-for-eggplant-blossoms-drying-out-and-falling-off.htm