ProductStore ANE's restoreTransactions( ) method returns Transaction objects with empty/null receipts

I am currently using the ProductStore ANE for iOS (which is a part of the Gaming SDK from Adobe) to implement In-App Purchases in my app.

I am able to retrieve products, and purchase products using the ANE, but when I try using the restoreTransactions( ) method in the iTunesConnect SandBox environment, it returns Transaction objects with empty/null receipt fields.

Is there something that can be done to rectify this? Or is this is the expected behavior of the SandBox environment?

Thanks in advance.