I purchased a two-pack game set at the Big Fish Games store, but cannot play one of the games. Why is that?
Simply speculating, it could be because the Big Fish Games: Game Manager wasn't working properly at the time or because one of the two games is not compatible with your current operating system. However, I would recommend contacting the company directly using the form found here: https://bigfishgames.zendesk.com/hc/en-us/requests/new as they will surely be able to assist you.
Don't forget to mention the names of the games that you bought, which one of them isn't working, the exact text of the error that you get (if any) and your PC's operating system.