Creating Custom Object in Salesforce Lightning using Selenium Webdriver - selenium

Question

I am trying to practice using Selenium by doing a simple operation of creating a custom object in Salesforce Lightning. My code works fine in Classic, but once I switch over to Lightning, for some reason it only works up to a certain point.
What works:
driver.get("http://login.salesforce.com");
driver.manage().window().maximize();
driver.findElement(By.xpath("//input[#id='username']")).sendKeys("<USERNAME>");
driver.findElement(By.xpath("//input[#id='password']")).sendKeys("<PASSWORD>");
driver.findElement(By.xpath("//input[#class='button r4 wide primary']")).click();
driver.findElement(By.xpath("//*[#id=\"oneHeader\"]/div[3]/div/div[2]/div/div/ul[2]/li[3]/div")).click();
driver.findElement(By.xpath("//*[#id=\"oneHeader\"]/div[3]/div/div[2]/div/div/ul[2]/li[3]/div/div[2]")).click();
So I am able to login and access the Object Create page just fine. The issue is with the next bit of code, which should be the easiest:
driver.findElement(By.xpath("//input[#id='MasterLabel']")).sendKeys("Address");
driver.findElement(By.xpath("//input[#id='MasterLabel']")).sendKeys("Addresses");
driver.findElement(By.xpath("//input[#value=' Save ']")).click();```
I keep getting the error message:
Exception in thread "main" org.openqa.selenium.NoSuchElementException: no such element: Unable to locate element: {"method":"xpath","selector":"//input[#id='MasterLabel']"}
Things I have tried:
Searching for the input boxes via name and id instead of xpath. Same results
Tried implementing an explicit wait. Doesn't seem to make a difference
Tried doing a driver.switchTo().frame() method, but Webdriver can't seem to detect an iFrame on the
page.
Any help would be greatly appreciated! Thanks