{
    "eventName": "dht-logger-log",
    "url": "https://YOURENDPOINT.execute-api.us-east-1.amazonaws.com/prod/iot",
    "headers": {
        "x-api-key": "YOURAPIKEY"
    },
    "requestType": "POST",
    "json": true,
    "mydevices": true
}
{
    "eventName": "dht-logger-log",
    "url": "https://YOURENDPOINT.execute-api.us-east-1.amazonaws.com/prod/iot",
    "headers": {
        "x-api-key": "YOURAPIKEY"
    },
    "requestType": "POST",
    "json": { 
        "from": "particle"
    },
    "mydevices": true
}

Change json field to have one field
Change json field to have one field

Having `json: true` used to work to ensure a `text/json` Content-Type.

Now it needs something in the payload, so let's use `"from": "particle"`