Empty message content when using Clickatell test template

Question

I am trying to make use of Clickatell's test template for Whatsapp push notifications but am receiving an error in Postman when parsing the payload as per the documentation. Response is a 202.

We have used the below payload with an actual Whatsapp number. We do have an account with Clickatell as we use this for our Lex bot. I have tried a different template as well. The below is what currently occurs, whereas we are expecting a successful response and a message via Whatsapp.

    {
        "messages": [
            {
            "to": "27xxxxxxxxx",
            "channel": "whatsapp",
            "template": {
                "templateName": "scheduled_payment_reminder_demo",
                "body": {
                    "parameters": {
                        "1": "Parameter 1"
                    }
                }
            }
        }
    ]
}

Below is the response:

    {
    "messages": [
        {
            "messageId": null,
            "accepted": false,
            "to": "27xxxxxxxxx",
            "error": {
                "errorCode": 100,
                "error": "Empty message content."
            },
            "clientMessageId": null
        }
    ]
}

When we add content as per below, the response is still a 202:

    {
    "messages": [
        {
            "to": "27xxxxxxxxx",
            "channel": "whatsapp",
            "template": {
                "templateName": "scheduled_payment_reminder_demo",
                "body": {
                    "parameters": {
                        "1": "Parameter 1"
                    }
                }
            },
            "content": "Hello"
        }
    ]
    }

    {
    "messages": [
        {
            "messageId": "xxxxxxxxxxxxxxxxxxxxxxxxxx",
            "accepted": true,
            "to": "27xxxxxxxxx",
            "error": null,
            "clientMessageId": null
        }
    ]
    }