Reporting
Squash
The most common reason for this problem is lack of pollination. There are female and male flowers. Sometimes the females bloom before any male flowers have bloomed and so the female flowers do not get pollinated. Usually, if you wait, you'll find that the males start blooming and you're getting TONS of squash! If not, there's a lack of pollinators in your garden and you can do it yourself with a Q-tip.