The only thing I can think has happened here is that you have (by luck or judgement) managed to find and try to use ATMs that are not connected to the international network.
That certainly used to be a "thing" in Brazil until relatively recently. I remember first time I went to Rio (20+ years ago) being directed to certain branches of CitiBank, precisely because they were then one of few banks connected to the international ATM network. Much more recently than that, I remember trying to use Santander ATMs, in a branch, and none of them were connected to the international network. Banco do Brasil sticks in the mind as being a solely national network - I don't think I have ever successfully used an international card to take cash out of a Banco do Brasil ATM. Branches of most large banks will have at least one ATM that does work with international cards - the distinguishing feature used to be the international ATMs had the Visa and Mastercard logos and the domestic ones didn't. The ATMs at GRU would have to work with international cards, considering where most potential users are coming from.