After announcing last week that iOS 8 will be released to the public on September 17th (that's tomorrow), Apple invited developers to begin submitting their apps and app-updates for the new firmware. In fact, it's already approved a number of iOS 8-optimized apps into the App Store.
But there's a problem that you've probably noticed if you're running a beta version of iOS 8 right now: extensions for many iOS 8 apps aren't working properly. According to MacRumors, the issue seems to be related to code-signing on Apple's end, and it's currently working on a fix.