I get this message({"message":"Payment amount must exist and not be negative."}) on using this below API to make payment using custom Tender.
POST
/v3/merchants/{mId}/orders/{orderId}/payments
I provide the details(Parameters)
{ "employee": { "id": "S48JPDMXXXX7W" }, "order": { "id": "17SYWXXXJBQPY" }, "tender": { "instructions": "erter", "visible": true, "editable": false, "id": "2GQ9XXXXXRGRY", "label": "Coupon", "labelKey": "com.bluepumpsoftware.application", "opensCashDrawer": false, "supportsTipping": false, "enabled": true }, "amount": "2243" }