From a Coffee I Couldn’t Buy to a Troubleshooting Lesson

I finished an article this morning about Bookplate, the café inside the National Library of Australia, and then headed out from home. I also threw my roller skates into the car because I had not skated there for quite a while. The weather was unusually pleasant. By midday the sun felt warm, and while skating I could already sense something slightly spring-like in the air.

Afterwards I went into Bookplate. Since I had just spent the morning writing about the café, it seemed natural to sit down and have a coffee there.

I tapped my phone on the payment terminal.

Declined.

I tried again with my watch.

Declined again.

There were people waiting behind me, so I let them go ahead while I stood to one side and opened my banking website. I had bought airline tickets this month and had spent more than usual, so my immediate assumption was that I had run into some kind of credit limit problem. Without looking very carefully, I increased the limit and tried to pay again.

Declined.

So much for the coffee.

I found the situation slightly ridiculous. I had written an article that morning recommending Bookplate, then arrived a few hours later and discovered that I could not even buy a coffee there. Perhaps, I thought, today was simply not the right day to write about Bookplate.

I tried calling the bank, but getting through was almost impossible. I then decided to go to McDonald's and test the payment again. Before using the McDonald's app, I tried paying directly with my phone at the terminal.

Declined.

Then I opened the McDonald's app, ordered a simple meal and paid with exactly the same bank card.

The payment went through immediately.

That was when the problem became interesting.

While eating, I started analysing it with AI. If an in-app transaction using the same card succeeded, the card account itself and the available credit were probably not the main problem. If both my phone and my watch failed at physical payment terminals, a simple NFC hardware fault on one device also seemed unlikely.

The terminal was also returning a definite declined response. From the customer's point of view, contactless payment looks almost instantaneous. You tap the phone, hear a sound, and the transaction is finished. Underneath that apparently simple action, however, several exchanges may already have taken place between the device, the terminal and the payment system.

If the terminal had progressed far enough to return a decline, the failure was probably occurring somewhere further along the authorisation chain rather than in a crude breakdown of communication between the phone and the terminal.

AI and I continued eliminating possibilities. The obvious next experiment was to use the physical bank card. If the physical card worked, the problem would probably be confined to the mobile-payment path. If the physical card also failed, then the bank's authorisation system or some broader payment problem would become much more likely.

By the time I finished eating, I felt that I had a reasonably good troubleshooting plan.

Then another thought suddenly occurred to me.

I had done exactly what I have been trained to do for most of my professional life. I had gone straight into the technical structure of the problem.

After many years working in technology, my instinct is to trace a failure through a system. Which stage succeeded? Which stage failed? What variables can be eliminated? What is the smallest experiment that would distinguish between two competing explanations?

There is nothing wrong with that approach. Most of the time it is extremely useful.

But this incident was slightly different. My phone and watch were both failing. The same thing happened at different merchants. The bank's telephone service was unusually difficult to reach. These were already signs that this might not be an ordinary fault involving one device or one card.

In a situation that unusual, perhaps the first step should not have been to dig further into NFC, card settings and payment protocols.

Perhaps I should simply have looked outside the system.

So I asked AI to check whether there were any reports of payment problems that day.

There were. ABC News reported that day that Mastercard was down because of what banks described as a “global issue”, with many Australian customers having their Mastercard payments declined.

At that point, much of my careful technical reasoning suddenly became secondary. My phone had probably not broken. My watch had probably not broken. My card settings might not have been the issue either. A larger system outside my own little troubleshooting diagram was having trouble.

The experience reminded me of a habit that technical people can easily develop. Logical fault isolation is useful, but before beginning it, we should first ask what kind of event we are looking at. If something is highly unusual and several apparently independent parts of the system fail at once, checking whether the external environment has changed may be more efficient than immediately examining our own equipment.

Troubleshooting does not only mean tracing inward through a system. Sometimes the first useful move is to look outward and see whether the system itself has changed around us.

On the drive home, I kept thinking that the whole episode was amusing enough to record. Just before reaching home, I turned off towards a nearby club. I thought I would sit down, have a coffee and write about what had happened.

Only when I was about to pay did I suddenly remember something rather obvious.

The entire afternoon had been about the fact that I could not pay for anything.

I had somehow forgotten that I still needed to make a payment in order to buy the coffee.

Fortunately, this time I tapped the phone and the transaction went through.

So I finally got the coffee I had been trying to buy all afternoon, and I could sit down and write this article.

It reminded me of the old joke about a power cut. There is nothing to do, so perhaps you should watch television. Except, of course, if the power is out, how are you going to watch television?

The mind can work in much the same way. I had spent the whole journey thinking about a payment failure, yet the moment I returned to an ordinary everyday action, I briefly forgot that the problem might still be there.

Fortunately, by then it wasn't.

And I finally got my coffee.