Python selenium send_keys not working on password field

Question

send_keys() works with the username field but not the password field. Here is my code:

class PpeLiveTest(LiveServerTestCase):


    # test that the first cell for the tennessee total row is the correct sum 
    # for quince and allenbrooke for the incentives table

    def test_sums_incentives_tennessee(self):


        options = webdriver.FirefoxOptions()
        options.add_argument("--headless")

        driver = webdriver.Firefox(options=options)

        driver.get('https://[redacted]/pr-run-ppe?group=MS%2FTN%2FLA&check_date=05%2F01%2F2022')

        # login first

        username_element = driver.find_element_by_id('id_login')
        username_element.send_keys('[redacted]')

        password_element = driver.find_element_by_id('id_password')
        password_element.send_keys(os.environ.get('ADMIN_PASS'))

        login_button = driver.find_element_by_xpath('/html/body/div/div/div/form/button')
        login_button.click()

I look at driver.page_source in the console when running this test. It's still the login page. username is filled with the [redacted] as expected but the password field is blank. Anyone know why?

os.environ.get('ADMIN_PASS') is not blank.

password_element is the correct element that we expect