Hdmi adapter will not play video from YouTube, amazon etc on iPhone SE (2016) Or XS

I’ve bought An hdmi adapter from the apple store and all works fine mirroring the phone, it will show my photos and it will show video that I have taken on my phone. It will also fun some of my apps that I want it to do and it shows them in full screen.

what it won’t do is mirror video from YouTube, amazon video etc. It only plays the sounds through the tv, both the phone and the tv are blank. At first I thought it was a security thing or maybe a cable issue so I tried my iPad and that works fine. It’s only my iPhone SE that won’t play video. So then I figured it was my phone, so I tried my other half’s iPhone XS and that does the same thing, blank screen with no video only sound.

its a genuine adapter from the apple store

its plugged into a genuine charger

its a high speed 4K HDMI cable

iPad works fine, iPhones do not