Unable to retrieve token bearer, error 99 Unable to verify your credentials

[Mb42Tc43]

I keep getting an error 99 for application-only authentication in node.js, and looking at the other articles seems to have not yielded any help. My code is shown here:

var request = require('request');

var options = {
  url: 'https://api.twitter.com/oauth2/token',
  method: 'POST',
  headers: {
    "Authorization": "Basic " + new Buffer("[key]:[secretkey]").toString('base64'),
    "Content-Type":"application/x-www-form-urlencoded;charset=UTF-8"
  },
  body: "grant_type=client_credentials"
};

request.post(options, function(error, response, body){
  console.log(body);
});