getting google oauth to work with flask, react, postgresql. keep getting internal server error and cors errors

I'm trying to get google oauth to work with flask and react. When I run the server and try to log in, the google sign-in window pops up and immediately closes down and I get an internal server error. in my flask terminal I get this error: raise MissingCodeError("Missing code parameter in response.") oauthlib.oauth2.rfc6749.errors.MissingCodeError: (missing_code) Missing code parameter in response.

Any thoughts?

app.py

  @app.route('/login', methods=['POST'])
  @cross_origin()
  def login():
  google_provider = get_google_provider()
  auth_endpoint = google_provider["authorization_endpoint"]

  request_uri = client.prepare_request_uri(
      authorization_endpoint,
      redirect_uri=request.base_url + "/callback",
      scope=["openid", "email", "profile"]
  )

  return redirect(request_uri)

  @app.route('/login/callback', methods=['GET', 'POST'])
@cross_origin()
def login_callback():
  code = request.json.get("access token")
  print("**************")
  # print(list(request.args.keys()))
  print(request.json)
  print("**************")
  token, headers, body = client.prepare_token_request(
  token_endpoint,
  code=code,
  authorization_response=request.url,
  redirect_url=request.base_url
  )
  token_response = requests.post(
      token_url,
      headers=headers,
      data=body,
      auth=(GOOGLE_CLIENT_ID, GOOGLE_CLIENT_SECRET)
  )

  client.parse_request_body_response(json.dumps(token_response.json()))

  userinfo_endpoint = google_provider["userinfo_endpoint"]
  uri, headers, body = client.add_token(userinfo_endpoint)
  userinfo_response = request.get(uri, headers=headers, data=body)

  if userinfo_response.json().get("email_verified"):
      unique_id = userinfo_response.json()["sub"]
      user_email = userinfo_response.json()["email"]
      user_picture = userinfo_response.json()["picture"]
      user_name = userinfo_response.json()["given_name"]
      user_member_since = datetime.today().strftime('%Y-%m-%d')
  else:
      print("User email not available or not verified by Google")

  user = User(id=unique_id, name=user_name, email=user_email, picture=user_picture,     member_since=user_member_since)

  if not User.get(unique_id):
      User.create(unique_id, user_name, user_email, user_picture, user_member_since)
      login_user(user)
      redirect(url_for("/new-user-form"))
app.js

  googleResponse = (response) => {
const tokenBlob = new Blob([JSON.stringify({access_token: response.accessToken}, null, 2)], {type: 'application/json'});
const options = {
  method: 'POST',
  body: tokenBlob,
  mode: 'cors',
  cache: 'default'
}
fetch(`${BASE_URL}/login/callback`, options).then(r => {
  if (r.headers.get('Content-Type') === 'text/html; charset=utf-8') {
    console.log('error')
    return 
  }
  const token = r.headers.get('x-auth-token')
  r.json().then(user => {
    if (token) {
      this.setState({isAuthenticated: true, user, token, message: `${user.name}`})
      console.log(token)
    }
  });
 })
}

onFailure = (error) => {
  alert(error.data)
} 

 <Route path='/login'>
          <GoogleLogin
            clientId={config.GOOGLE_CLIENT_ID}
            buttonText="Login"
            onSuccess={this.googleResponse}
            onFailure={this.onFailure}
          />