I had the same thing happen to my Onesmart card.

3 days into a US holiday it stopped working. When I rang them to ask why they said they had noticed increased activity and it was outside NZ.

I was somewhat confused since this is sold as a travel card and I had loaded up US$ onto it for this trip. Once I talked to the person they unlocked it and I didn't have any issues for the rest of the trip.

In my case it got declined at a shop and I paid cash for the item so luckily it wasn't too bad.