The baskets are marked as reversed, the subscription is expired at CBSubs and needs to be reactivated, BUT the subscription is not expired at Stripe and stays active with renewed or payments each future months without CBsubs knowing it.

A reversed state should tell Stripe to pause the subscription. So the subscription should still exist perfectly fine, but be paused. We do this using the below API.

​​​​​​​https://stripe.com/docs/api/subscriptions/update#update_subscription-pause_collection

You should see the subscription update call in Developers > Log of your Stripe dashboard when the dispute was made.

If CBSubs expires the subscription and reverse the payment, shouldn't it also send an info to Stripe to cancel the subscription there ?

It's not expired. It's reversed. We don't cancel until the dispute is handled (either won or lost) and until then it's considered a pending state.

It sounds like the payment is going into dispute and for whatever reason the user goes and tries to subscribe again resulting in the double Stripe subscription issue.

If you want Stripe to cancel recurring subscriptions on disputes instead of waiting for dispute resolution then configure it to do so. Specifically in your Stripe dashboard go to the settings page then navigate to Billing > Subscriptions and emails next under "Manage disputed payments" adjust it however you like. The default leaves the subscription alone, but if you want it to instead cancel you can do so here. You can also manage how payment retries are handled here.

I understand, but for SEPA payments (90% of our customers) there is no handling as the dispute is always lost contrary to credit cards dispute. So the basket shows as reversed and the subscription is expired

That should be sending a dispute lost webhook then. If not then that'd be an issue at Stripe not sending it.

So in this case, CBSubs will expire the subscription, Stripe will cancel it and our mods can trigger a new subscription, correct ?

Correct.

Did you implement a way to reuse the basket to trigger a new payment for the customer if the first payment failed ? 

No.

During a dispute CBSubs only pauses collection. If the dispute is won it will resume. If the dispute is lost it will cancel. If the dispute is never handled then it's going to stay paused. This is done by listening to the following Stripe webhooks.

Disputed
Event: charge.dispute.created

Dispute Won
Event: charge.dispute.closed
Status: data.object.status of "won" or "warning_closed"

Dispute Lost
Event: charge.dispute.closed
Status: data.object.status of "lost" or "charge_refunded"

Review the webhooks for that payment and see what status Stripe is sending to your site. Should also be able to see the notification in CBSubs > Notifications.

You can configure how Stripe handles subscriptions for disputed payments. Within your Stripe dashboard click Settings followed by Subscriptions and emails then scroll to "Manage disputed payments". Change "Subscription status" to "cancel the subscription immediately without prorating" and it will immediately cancel the subscription if a recurring payment goes into dispute.