Hello,
Unfortunately, due to a rework of our purchase system in the last update, we decided to discontinue this legacy offer.
The SOFIA offer had been available since November 24, 2014 (over 9 years), and required additional custom code for this offer to be supported.
As the app stores change, we have been required to update our purchase code implementation to continue being compliant with the App Store/Google Play requirements. Keeping support for this legacy offer involves additional development and testing, which is hard for us to keep up with, especially for an app like Infinite Flight that has been maintained since the initial launch on iOS/Android.
We do appreciate your business and hope you continue to get value out of our new features and content.