Chances are if you're running a Nintendo Switch and hate their voice chat system on your phone, you've probably installed Discord either on your device or on your PC to better communicate with people. Even if you're not gaming, it makes for a good free communication system that's clearer than Skype if you're just going for audio. However, if you're currently using an iPhone do this, you're probably not anymore. Among the problems that the latest iOS update caused people, iOS 11 has created an issue with the Discord app not allowing it to work.
At the moment, Discord is aware of the issue and are working to remedy the issue, but a timetable hasn't been set by the company yet. This isn't the first time Apple's updates of the iOS system have caused apps to fail, even when they receive notice ahead of time. One notable issue that is still ongoing is the free Shakespeare app that causes plays to become stuck on a single page. Or when Photoshop Express had issues allowing photos to be seen in their app. But like those examples, this is simply an error where the app is busted and not completely dead in the water.