Selenium: NoSuchElementException: Unable to locate element

find_element searched the current browsing context and nothing matched the locator at that moment. The JSON at the end shows exactly what the driver searched for. Note that By.ID, By.NAME and By.CLASS_NAME are translated into CSS selectors, so the method usually reads css selector even if you did not write CSS.

Without an implicit wait, find_element checks once and throws immediately. On pages that render with JavaScript, the element often appears a moment later, which is why this exception is so often a timing problem rather than a wrong locator. The other common causes are being in the wrong context (the element is in an iframe, a shadow root or another window) and the page simply being different from what you expected.

What is not wrong: the browser or driver setup. The session works; the search came up empty.

from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC

wait = WebDriverWait(driver, 10)
wait.until(EC.frame_to_be_available_and_switch_to_it((By.ID, "auth-frame")))
username = wait.until(EC.visibility_of_element_located((By.NAME, "username")))
username.send_keys("demo")
driver.switch_to.default_content()

Use explicit waits for anything that appears after page load, and avoid mixing implicit and explicit waits, which Selenium's documentation warns can cause unpredictable wait times. Prefer stable attributes such as IDs, names or data-testid over generated class names. Make frame and shadow-root switches explicit in page objects.