Add paragraphs to a node via jsonapi
Did you gave node type ? Try the following body data. 

{
 "data": 
  {
     "attributes": {
            "title": "title of your new node", 

        },
         "relationships": {
            "field_body": {
                "data": {
                    "type": "paragraph--text",
                    "id": "b0247bf8-a3c0-4a45-8e05-4f4901011000"
                }
            }
        },
      "type": "node--yournode"
    }
  }