Hi there,
Been using my Monzo card for a few days and ran into an issue when trying to use Papa Johns online ordering system. I twice tried using it to make a purchase only to receive an error stating there was an error with the payment (on the papa johns website). On the monzo app I could see the funds being transferred to papa johns then immediately refunded.
That’s a strange one, I’d recommend contacting the support team via the in-app chat or by sending them a DM on Twitter, to find out what’s happened there.
It would be great to hear the explanation 
Is it trying to use MasterCard SecureCode and failing at that point?
Papa John’s defo accepts Monzo cards as I have purchased from them before.
This was all completed via a web browser on my pc btw - I didn’t seem to actually get the mastercard securepay splash screen - after hitting the pay now button the screen seemed to refresh after 1-2 seconds and then displayed in red text that the payment couldn’t be processed - potentially a PJ issue?
That said I paid with my other debit card and this worked fine.
The screen refresh would be the Arcot Systems “3D Secure” page. Maybe for some reason the 3D secure is declining the transaction? (though that would surprise me - officially Monzo doesn’t have 3D secure so I assume it would always approve)
You are kinda right, but it depends… In usual integrations, merchant checks if 3d secure is offered for a card. If yes - they show 3d secure window. If nope - they continue without it. That’s the most common integration logic.
However, some merchants choose to automatically reject transaction if user has a card without 3d secure enabled. After successful 3d secure check, responsibility for fraud is shifted to a bank - if customer claims they didn’t make the purchase, but 3d secure was completed, then merchant doesn’t need to give the money back. I may be oversimplifying, but more or less that’s the whole point of not allowing any transactions without 3d secure enabled & successful.
While I don’t know if that’s the case with Papa John’s, we had some reports that Monzo wouldn’t work with those merchants that force 3d secure (don’t chase me for links, I had seen it scattered in multiple places and I don’t remember keywords to search for). 
Happened again the other night!
Bizarrely the card also failed earlier today when I tried to make a contactless payment at a train station ticket machine which had previously worked on a couple of occasions.