I'm a technically competent person, but I come from a time when to pay for parking you put coins in a machine and it either:
a) gave you a ticket, with that special adhesive that was really hard to clean off your car window, but would cause the ticket to fall off 5 minutes before the traffic warden came round
b) let you out through a barrier
I drive so infrequently that whenever I encounter one of these 21st century ways of paying for parking I get extremely flustered. Bonus points if it requires me to know the registration number of the car I've just been driving.
My wife is a technically competent person too, and I feel a bit mean dobbing her in for this one - after all, there but for the grace etc.
Her mistake was to pay for the car park that the app presented to her, and not check that it corresponded with the car park she was in. The one she paid for was one she had visited about a year previously, so obviously that was the last one in her search history. Easy enough error to make.
Around here they use one of the fifty-two available parking apps, all different yet alike, that will require you to identify your car park from a list of 64 nearby or input a number that you can't find. Once you've done this and input your car's registration number you'll find that there's is almost a mobile signal. The result is that you'll spend another ten minutes in the car waving your phone around in the hope of attracting a confirmatory message from the ether.
There's a local car park that used to be free until fairly recently. Then suddenly signs appeared to say you had to pay, but no physical ticket machine, it all had to be done via Ringo or somesuch. Of course, this car park is in the middle of a remote woods with no residential area nearby, hence no mobile phone masts...
On my most recent visit to this car park, it had reverted to being free.