Authentication on Drupal 7 website not working

Attempting to sign up for newsletter on organization website results in "Sorry, there was a problem, please ensure your details are valid and try again." Have confirmed username and password multiple times (am currently logged in here successfully).

Website is Drupal 7 using this module to connect to API: https://www.drupal.org/project/constant_contact

Have reported this issue on Drupal module issue list as well https://www.drupal.org/project/constant_contact/issues/3189719

Please advise.