Cesium ion get token 409

I wang Connecting to Cesium ion with OAuth2,but when I get Code Authorization,send https://api.cesium.com/oauth/token Obtain Token return POST https://api.cesium.com/oauth/token 409。
my request:
url: ‘https://api.cesium.com/oauth/token’,
data: {
grant_type: ‘authorization_code’,
client_id: 194,
code: 20d139f5b08fe3fd4aba735dc30535b4cb154f268ba7dcfd32c4f53987b8e7f754a129d37a2c882576e44ae812a9aa69768aa2d67db38c57c09b17834a8ed9fc,
redirect_uri: ‘http://localhost:4400/index’,
}).then((res) => {

  // localStorage.setItem('cesiumIonCode', to.query.code);

Welcome to the Cesium community!

Can you point me to the API call that you are using from our Cesium ion API documentation?