I have button called 'sign in' and that button redirects to a sign in screen into a new tab where I need to enter username and password using selenium sendKeys method.
But it keeps saying: *'no such element'*. Please help me. What am I doing wrong?

```
driver.get("https://example.com"); 
driver.manage().window().maximize(); 

//This button redirecting to a new url into new tab
driver.findElement(By.className("click_sign_in_button")).click(); 

driver.findElement(By.id("username")).sendKeys("abc@gmail.com");
driver.findElement(By.id("password")).sendKeys("1234");
driver.findElement(By.className("login")).click();

```