If a renewal charge fails, nothing breaks immediately. A banner appears in the console telling you the payment failed, and Stripe retries the charge automatically over the following days.
What to do
Go to Account → Billing → “Manage subscription” and update your payment method. The next retry then usually succeeds on its own.
If it keeps failing
After the retries are exhausted, the subscription is cancelled and the account drops to the Free plan. Your templates, outputs, and settings are all kept. Resubscribe any time and everything picks up where it left off.