https://public-api.gohighlevel.com/#1e0867c3-69da-4240-9427-e1286b79472f Got the headers in there etc? You do need all these for it to work too: { "calendarId": "CVokAlI8fgw4WYWoCtQz", "selectedTimezone": "Asia/Calcutta", "selectedSlot": "2021-06-23T03:30:00+05:30", "email": "john@deo.com", "phone": "+18887324197" }