I think it depends on the station. I've never had any trouble online, in any of the big Paris stations, or in any manned station, but . . . once in a small suburban station, the machine couldn't/wouldn't make change and none of us had 3,35 in coins. The machine wouldn't accept any of our non-chipped cards---and we had a bunch of them. Finally, I dredged a Carte Bleu out of the bottom of my purse and bought tickets for all of us. I think it's just a glitch in the system, like carnets at the Hotel de Ville manned station---they always seem to have some sort of demagnitization problem if bought there and have to be replaced.