Looks like something is attacking the flowers at the base where they attach to the vine, so they fall off. I can see what looks like little bite marks.
Flowers of Passionfruit Vine Dropping Off
Common causes of blossom drop in any fruiting plant are failure in pollination, or too many flowers to support, or not enough sun or water. One thing that comes to mind when you say little tooth marks is mice. Also, there is a possibility of bugs (thrips?) or some disease. You can look carefully on the existing flowers, and the branches and leaves for any kind of bug; you can also take some samples to the nearest Extension Service for analysis; this link will help you find one: https://www.gardeningknowhow.com/extension-search/
FYI, here's rather a lengthy article on passion fruit that might be of interest to you; https://www.hort.purdue.edu/newcrop/morton/passionfruit.html