Dock Connector not working after iOS 12 update

Prior to updated a few weeks ago I was able to “mirror” my iPhone 6s to my tv to watch YouTube, movies, sporting events from apps etc... now I plug in my dock connector (lighting to hdmi) into my iPhone and I am able to see my phone on the tv till I play video the screen will go dark on the tv and still play audio but no video. Does the same in portrait or landscape, doesn’t matter how I turn the phone. I have tried to start the video before plugging in the phone and when I plug it in it immediately goes dark, with no video but audio sounds fine. Any ideas on a fix or confirmation that the update has caused the issue? Thanks for any response in advance! I am tired of racking my brain for a fix.