subscription_not_cancelable
HTTP 409, type conflict_error.
The subscription is in a state that cannot be canceled.
Why it happened
The message names its current state. This code is raised for an immediate cancellation, cancel_at_period_end: false, of a subscription that has already ended: expired or terminated. A subscription that is already canceled answers the cancel with its current state instead of this code.
How to fix it
Read the state in the message. If it is expired or terminated, the subscription has already ended and stopped billing, and there is nothing to cancel.
Retrying: do not retry the same request. It will not succeed.