Ask HN: Stripe payments being declined for existing customers, what can I do?

We have noticed that many cards are being declined (with generic "card_declined" error code) even for existing customers whose payments initially went through. This issue has started occurring with different banks in various countries. It has been happening since September 20, and we are losing our existing subscriptions. Stripe support said they can't do anything about it. Has anyone else experienced this? What can I do in this situation?