Shuffle feature failure

After already purchasing the questions ~1 year ago, I shuffled the questions today on my iPad and was prompted to buy set II for $80, which I did. Everything seemed to be working, so I tried the app on my phone. Again, when I tried to shuffle the questions I was prompted to pay $50 for question set III. Everything seemed to be working on my ups for now, but how many question sets do I need to buy before I can randomize?

Bobarooniey about Anesthesia Comprehensive Review