My dunning configured to cancel the subscription after 10 days.
However, some subscriptions were not canceled (ex: https://invoicesimple.chargebee.com/subscriptions/9236547/details)
What is even stranger is that I collected manually the two oldest invoices and it worked, despite the expired card.
Thanks for posting!
Dunning for invoices would work only when auto-collection is turned on. For the subscription that you've shared with us, it looks like auto-collection is turned off which is why dunning didn't kick in.
Auto-collection can be controlled at both the subscription and customer level. This comes in handy when a customer has multiple subscriptions and you would like to automatically collect payments only for specific subscriptions.
Note: Auto-collection would be turned on automatically if a payment method is added.