Update your card and billing details from the Stripe Customer Portal, which you open from Settings → Account.
Steps
Go to Settings → Account.
In the Subscription Plan section, click Open Customer Portal.
In the portal, update your payment method or billing address, or view invoices.
Save. Changes take effect immediately.
What to expect
The Open Customer Portal button only appears for the account owner. If you're a team member, ask your account owner to make the change.
If you're the owner and don't see the button, for example after a failed payment, email [email protected] for a link.
The portal is hosted by Stripe, Doorkeep's payment processor. You may be asked to confirm your details there.
A card update won't change your plan or billing date. It only changes how you pay.