@purple1976 Did you remember if you're connected to any WiFi when first time you discover the icon? If you're in the same network as a Chromecast's network, then you'll be able to see the icon. That's the only reasoning I can think of right now.
I have read on other forums that other people have had this and can then play on their phone until the point when the app is restarted. Might be Google testing out a range of phones without releasing it in general?