cm

[swift kindle]

You should be able to update the existing subscription with an API call. Or is there a reason that that isn't viable here? https://stripe.com/docs/api/subscriptions/update#update_subscription-payment_settings-payment_method_options-card-request_three_d_secure

Also, not sure how likely this is, but the user's bank might not request 3DS here. They are much more likely to if you turn that setting on, but banks can always decide not to request 3DS even when you do. I don't think that is particularly likely, but if you have that setting on and 3DS still isn't being requested, the user would need to reach out to their bank to ask why it isn't happening.