I had several instances of that in NZ, so after the second refusal, I contacted my bank (Santander) in the UK to ask what was going on, as they knew I was in NZ. The response was that there had been no attempted transactions. I also had a rash of it in France*. One can only surmise that some furrin' machines go "ooh, a furrin' card, dunno what to do with that, so I'll just claim it was refused." I get the impression that most other countries have even more backward banking systems than our own.
* I did also have a nasty rash in France, but I'll try not to mention it again.