Auto generating posts with iOS App

First off I know there already exists an iOS app but I am creating my own that will be able to take photos and upload them to our website. I am having issues with auto generating posts using wp_insert_post and was wondering if anyone has experience doing anything like this and could lead me in the right direction. Basically I have a php script that uses wp_insert_post that works but when it is called by the iOS app it doesn’t run.

Any help would be great

Thanks