Yahoo Mail App notifications not showing up

I use the Yahoo Mail App instead of the native iOS mail app, but as of a couple weeks ago, suddenly none of my mail notifications show up. All my settings are set to allow notifications, both in the app itself as well as in the Notifications area in Settings. All of the mail is there when I open the app, so it's not an issue of the mail not reaching the app, I just get no notifications in the lock screen when they do arrive.