Why isn't it showing my fertile days anymore?

All of a sudden, my calendar isn't showing my fertile days. I've put all this information onto this app for over a month and now it's useless. I've redownloaded it, checked my settings, and all of the obvious things to do. I'm very tech savvy and can't figure it out. I'm going to have to download another app and redo everything. Has this ever happened to any of y'all?