Error messages

Success: { "code": 0, "msg": "ok", "data": ... }

msg	Meaning
signature invalid	RSA2 verification failed
merchant not found	Invalid X-Merchant-No
merchant inactive	Merchant disabled
merchant request expired	Timestamp skew
merchant duplicate nonce	Reused nonce
merchant ip not allowed	IP whitelist block
merchant order no already exists	Duplicate merchantOrderNo
merchant order not found	Unknown order
merchant balance insufficient	Payout wallet balance too low
amount must be greater than zero	Invalid amount

Callback must return HTTP 200 and body OK or platform will retry.