Since the last recent updates made by Apple, there is compatibility issue with iOS5.1.1 affecting many existing apps in the App Store including Photon Browser.
Apple phased out of older devices and OS were new in the recent iOS 9 release. At the moment, Apple does not provide us with other means to provide our users using older devices with an older version. Our developers are not able to produce any version of the app for these older devices and iOS 5.
We understand that you had spent money on this and if you'd like a refund, we would encourage you to contact Apple using this link:http://support.apple.com/kb/ht1933.
Once again, we deeply apologize for this.