I am not able use App Store Promotions to promote my in-app purchases because the binary doesn’t include the SKPaymentTransactionObserver method as shown below:
These in-app purchases can’t be promoted on the App Store because your latest approved binary doesn’t include the SKPaymentTransactionObserver method.
The application is developed using Ionic4
There are two way for in-app-purchase in ionic, namely In App Purchase and In App Purchase 2. In principle, the implementation of In App Purchase don't support App Store Promotions and hence SKPaymentTransactionObserver method is not supported (still to date an open issue in the plugin repository issue 172).
To get the support for App Store Promotions the developer must use the In App Purchase 2 which supports the promotions as indicated in issue 608.