Opening first app on iOS

Hi. New to react native and found expo on their additional resources link. Looks exactly what I need and am excited to get going.

Created my first app and then thought I’d just test using the QR code. All worked great in Android, including hot reloading! So cool!

Tried the same on iOS and all I get is the browser opening the json manifest? Not the app? What am I missing to get it working on iOS?

Many thanks