Apple has tightened the security around launching external apps. For more background on these changes please read this post by Greg Pierce. As he states:
There are two URL-related methods available to apps on iOS that are effected: canOpenURL and openURL. Up until iOS 9, apps have been able to call these methods on any arbitrary URLs. Starting on iOS 9, apps will have to declare what URL schemes they would like to be able to check for and open in the configuration files of the app as it is submitted to Apple. This is essentially a whitelist that can only be changed or added to by submitting an update to Apple.
In order for these methods to work in iOS 9 developers need to update their app's plist with code similar to the following:
<key>LSApplicationQueriesSchemes</key> <array> <string>fbapi</string> <string>twitter</string> <string>whatsapp</string> </array>
Developers using Appcelerator Titanium will need to update their tiapp.xml file to fix the Ti.Platform.canOpenURL and Ti.Platform.openURL api calls in iOS 9.