refund for unused tickets

Hello,

A couple of days ago I was visiting the Netherlands and I was trying to buy train tickets for me and my friends using the ns app. The problem is that everyone time after I finished the payment I would get an error page and I wouldn't see a ticket in the NS app so we ended up buying tickets from the machines. 1-2 days later I got a notification that the payments had gone ahead and that I was charged. That's when I realized that I had gotten emails with the tickets, but they had gone to spam. The ns app malfunctioned, as usually after the payment had gone through it would show me my ticket (that's why I didn't have to check my emails). Is there a way to request a refund for these unused tickets?