For 400 errors, the error response will be in a JSON structure as shown below

     "success": false,
     "error": {
          "message": "Couldn't find a thing with that ID",
          "name": "NotFound",
          "code": 404

The Site Flow API returns a JSON error along with one of the following error codes:

Error Code Meaning
400 Bad Request – Your request had an error. Site Flow will usually return the reason for the 400.
401 Unauthorized – Your API key is wrong
403 Forbidden – Your API key doesn’t allow access to this resource
404 Not Found – The specified resource could not be found
500 Internal Server Error – We had a problem with our server. Try again later.
503 Service Unavailable – We’re temporarily offline for maintenance. Please try again later.