IPhone – How to view the transaction list for the debit card on Apple Pay

The "official" way to fix, per Apple, it is to email Apple's iTunes support (iTunesStoreSupport@apple.com), inform them of the problem, and then wait for them to fix it for you on their end. The good news about this solution is that my email was answered very quickly, the support person knew what the issue was and how to fix it, and within a couple days of telling them about the problem they had fixed it and I am up and working again.

After they told me it was fixed, it did take almost exactly 24 hours to take effect, and in the email they told me "wait about 24 hours and try purchasing an app again."

At the time I was having this problem (while traveling abroad) I was in no mood to "wait it out" as other answers have suggested, but since it was handled so capably and promptly by iTunes Support, I wouldn't suggest that as a course of action. It is a known issue for them.

The reason why you are getting these messages when your card is empty is that they are trying to make an authorisation hold to confirm your account details. It's standard practice. If you do see these small amounts appear on your card statements, you should see a similar transaction reversing the hold a short time later.

From Apple's support website:

If you update your billing information, the iTunes Store or Mac App Store will place an authorization hold on your payment card account, usually in the amount of 1 USD or the local currency equivalent, to verify your account information.

You might see authorization requests on your online statement. These requests aren't actual charges; they are tests to confirm that your payment card account is active and has available funds to accommodate transactions. Authorization holds are removed by your financial institution shortly after your purchase clears. The time it takes to remove authorization requests varies by financial institution.