I'm sorry, sometimes we all try too hard to be helpful.
You can't see any difference because there is no such thing as male and female eggplant flowers.
"Eggplants don't have separate male and female plants. Neither do they have separate male and female flowers. They are self-pollinating, meaning each flower has male and female parts and does not need another flower in order to produce fruit.
The following link has a pic showing the difference between male and female fruit. I have grown egg plant since I was a kid 35+ years and have known the difference. the Male fruit have less seed or smaller seed and are less bitter. The female fruit has a longer marking on the end of the flower blossom end of the fruit away from the stem. The male fruit has a smaller rounded spot. Some are difficult to distinguish. If you see ones at the market with a noticable longer slit mark where the flower blossom was attached leave that fruit on the shelf.
The plants produce both male and female fruit, both fruit are fine to eat, just that the male are usually less bitter.
g5 was on to something about heat extremes though. Eggplant will not set fruit in extremely high temps that is above 95F (35 C)
The wood ash was a good suggestion. One thing that can cause plants to get large and leafy but not set fruit (eggplant is technically a fruit as are tomatoes) is too much nitrogen, if you use high nitrogen fertilizer (or if the plant is next to a lawn and can receive runoff from the lawn fertilizer). Wood ash provides potassium which balances this off.
You didn't say much about what conditions it is in. It needs full sun to set fruit, at least 6 hrs. Avoid overhead watering which can knock flowers off, but it does need lots of water, 2" a week. It needs deep watering, where you let the water soak down and encourage the plant to grow deeper roots. So water infrequently but deeply.
Hope this is some help... let us know more about the conditions, weather etc that the plant is in.