Failed to send the mail via Sendgrid StatusCode:

400

Body:

{
  "errors": [
    {
      "message": "The content value must be a string at least one character in length.",
      "field": "content.0.value",
      "help": "<http://sendgrid.com/docs/API_Reference/Web_API_v3/Mail/errors.html#message.content.value>"
    },
    {
      "message": "The content value must be a string at least one character in length.",
      "field": "content.1.value",
      "help": "<http://sendgrid.com/docs/API_Reference/Web_API_v3/Mail/errors.html#message.content.value>"
    }
  ]
}