Edit:
The correct key to be used in the app's plist file is LSApplicationQueriesSchemes
and not UIDefaultLaunchStoryboard
as stated by Apple's documentation.
Original answer:
From Apple's documentation:
If your app is linked on or after iOS 9.0, you must declare the URL
schemes you want to pass to this method. Do this by using the
UIDefaultLaunchStoryboard array in your Xcode project’s Info.plist
file. For each URL scheme you want your app to use with this method,
add it as a string in this array.
If your (iOS 9.0 or later) app calls this method using a scheme you
have not declared, the method returns false, whether or not an
appropriate app for the scheme is installed on the device.
You can read more about it here.