I am getting 406 error on adding product metafields using POST API. Please help!

[jinu1992]

function METAFIELD_UPDATE_TEST()

{

  var headers_test = 

    {

    "Content-Type" : "application/json",

    "Authorization": "Basic " + Utilities.base64Encode(api_key + ":" + api_pass)

    };

  var product_id = 6648411324502;

  var dimensions = "lxbxh"

  var store_url= 'https://cubelelo-cube-store.myshopify.com/admin/2021-07/products/'+product_id+'/metafields.json';

  var post_dimensions= {"metafield":{"namespace":"my_fields","key":"dimensions","value":dimensions,"value_type":"string"}}

  var payload1 = JSON.stringify(post_dimensions);

  Logger.log(store_url);

  Logger.log(payload1);

  var params1 = {"method" : "PUT","headers" : headers_test,"contentType" : "application/json","payload" : payload1}

  var response1 = UrlFetchApp.fetch(store_url, params1)

  Logger.log(response1.getContentText()) 

  return "UPDATED";

}