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The "Attempt payment collection when the payment method is added" option works only when there is an unpaid invoice on the customer record. In this case, since the customer was in a trial period and there are no invoices attached to the subscription when the payment method is added, there are no invoices to attempt the collection.
Also, we do not automatically reactivate the subscription in the case of cancelled subscriptions since there is a possibility that the customer is uploading the card to pay for the unpaid invoices and not reactivate the subscription. You can use the Reactivate subscription option on the subscriptions page or call the "Reactivate a subscription" API to reactivate the subscription.