instrument_unavailable
HTTP 409, type conflict_error.
That payment instrument could not be saved.
Why it happened
The card was found, but it could not be attached to the customer within the same request: it changed or was removed while the save ran. The save did not take effect. Nothing was charged.
How to fix it
Try again with a new Idempotency-Key. This refusal happens after the key is claimed, so the same key will not run the request again. If it repeats, contact support with the request id.