Hi Dan,
The receipt is not in my junk folder. When I do this with another purchase, e.g. “Random Content”, it opens with the receipt immediately in my browser:
However, not receiving the receipt is not my first concern. I was mentioning this so it might help you find the course to the issue.
My first concern is that I can not install Card Flip on my iMac anymore. When I try to install the Card Flip, it starts saying downloading, and then it stops, and nothing happens. Perhaps the attached video makes it clearer