I am writing this in hopes of helping others as I was having the same issue. I buy leaf dollars at least once a month, I have a valid form of payment on file, always have, and I occasionally buy apple gift cards to add to my account. However, I had tried to purchase leaf dollars over ten times this month on my iPad, the device I always play on. I will discuss my process and issues in hopes that everyone with this problem will have it resolved:
When I attempted to purchase leaf tickets, I got a message: Your Purchase Could Not Be Completed: for assistance, contact iTunes support.
I get an error message: An error has occurred. Please try again later. Support code [802-0-007-053-03A]
To test if this is a widespread in-app purchase issue or specific to Pocket Camp, I went into another game that I play. I was able to make an in-app purchase without issue. The issue is Pocket Camp and Pocket Camp alone. I contacted Pocket Camp multiple times and iTunes. Sadly, both of them was an extreme letdown and failed at helping me solve my problem. A lot of the "troubleshooting" is deflecting the facts, and they try to summarize it like one of the responses in this forum, "you need to have a valid form of payment on file!" If you read what people are saying, especially those who have bought leaf dollars multiple times, maybe don't assume that the issue is them. Anyway, this forum made something click in my brain. I noticed someone wrote with the same issue and mentioned that they had added funds to their account. Funds, to me, mean gift cards. I purchased a gift card (which I have plenty of times in the past, and it worked fine for leaf dollars), but I noticed a potential common denominator in what could be an issue. Anyway, I tried over 20 times to buy leaf dollars for two weeks. Finally, my monthly subscriptions slowly depleted my gift card, like I wanted to test my theory. As soon as my gift card was gone and I went to use my standard form of payment, my leaf dollar purchase was successful. Sadly, my theory and my troubleshooting solved my problem.
For anyone else experiencing this, if you are adding funds to your account, such as a gift card, if no money has been taken off it, contact iTunes and get them to remove the card and use a standard form of payment. Or, make other purchases to get rid of the gift card and buy your leaf dollars using a regular payment, not a gift card. I am not sure how this solution makes sense or why this situation occurred since I have bought iTunes gift cards multiple times for leaf dollars; however, my theory was correct, and I can now buy leaf tickets.