title: Cannot find web element on div popup when using nodejs and webdriverjs
body: <p>Please help me, I stuck at likely simple task. I'm learning to webdriverjs , so I wrote a small code to register an account on FitBit site at url: www.fitbit.com/signup, after input my email and password, there is an div popup show up and ask user to fill all required field. Problem comes here, I cannot 'sendkeys' or 'click' on First Name field, could you please help me out?</p>
  
  <p>my code is very simple:</p>
  
  <pre><code>const webdriver = require('selenium-webdriver');
  
  const driver = new webdriver.Builder()
      .forBrowser('firefox')
      .build();
  
  const By = webdriver.By; 
  
  
  // ask the browser to open a page
  driver.navigate().to('https://www.fitbit.com/signup');
  //Enter Email
  driver.findElement(By.className('field email')).sendKeys('thisisatest@yopmail.com');
  //Enter Password
  driver.findElement(By.className('field password')).sendKeys('Abcd1234');
  //Check check box
  driver.findElement(By.id('termsPrivacyConnected')).click();
  
  
  //Click Continue button
  driver.findElement(By.xpath("//button[@type='submit'  and @tabindex='16']")).click();
  
  
  
  //Input First Name
  driver.sleep(3000);
  
  driver.findElement(By.xpath('//input[@id="firstName"]')).click();
  driver.findElement(By.xpath('//input[@id="firstName"]')).sendKeys('why not input');
  </code></pre>