Hi, I found this thread doing a Google search for the issue with subscribe and save payments not going through.
I’m not a Monzo user but a Curve card user which allows you to use your Curve card as a front end for the payment allowing you to choose which back end card the transaction runs through with cashback and other rewards.
Anyway I have exactly the same issue and had Curve blaming Tesco bank and the bank blaming the Curve system but was interested to find the view of some of the more financially savvy users on this forum which suggested the Amazon transaction system to be a bit clunky from what I gather.
I looked at my payment settings in Amazon and noticed no card was set as the default. When I went to set the Curve card as default Amazon did an authentication to complete setting the card up as the default.
Does any of the savvy users of the forum think this might help?