Hi @Gorgardog5
Welcome to the Sonos Community!
Do I understand you correctly that you are trying to play YouTube videos on your iPhone with audio AirPlay-ed to your Sonos One stereo pair? And that the issue you are having is that the video won’t even start playing when AirPlay is connected?
What happens if you try to play something else on your iPhone? Do you then get audio?
Also, how are you starting AirPlay? Are you doing so from the iPhone’s Control Centre? If so, please try initiating AirPlay from within the YouTube app - that way, you’ll be using AirPlay 2 which should perform better.
I hope this helps.
"Common sense is the collection of prejudices acquired by age eighteen." - Albert Einstein