I have an iPhone 5s and ever since I updated to iOS 8.1.3 I can't play videos. Online videos, such as YouTube, look like they're playing (the progress bar/timer moves) but it is just a black screen. Videos that I have recorded using the iPhone camera just won't start (the first frame of the video shows up on the screen, but no playback happens). Is anyone else experiencing this? Any ideas on fixing it?