The following scenarios exist for failed payments:
the user's account is not covered
the user has manually rejected the payment
the user's bank does not allow the direct debit
You can see exactly where the problem is in the status of the payment process.
for example if the status "Contestation lost" the best thing is to do is to contact your customer because the bank account may not be covered.
In the 3rd case, check the user's payment at Stripe for the mandate reference.
Then send the link you can find in the Payment Method in Stripe to the user concerned (this is your direct debit mandate). The user sends the link to their bank with the instruction to agree to it.
