iOS9: canOpenURL returning false for WhatApp's url scheme

In iOS 9 you must whitelist any URL schemes your App wants to query in Info.plist under the LSApplicationQueriesSchemes key (an array of strings):

For example:

So in your case, instead of fb and twitter you will have to specify whatsapp.

Note that this mechanism only applies to canOpenURL and not openURL. You do not need to have a scheme listed in Info.plist to be able to open it with openURL. Hope that helps.

In addition to @z22's answer if you need to add it textually (e.g. with Xamarin) then it looks like this:

    <dict>
        ... 

        <key>LSApplicationQueriesSchemes</key>
        <array>
            <string>whatsapp</string>
        </array>
    </dict>