It depends which login user interface you were presented. If I go to southwest.com and click "Log in" I don't have any problems. If I try to go directly to a page only available to logged in users (such as https://www.southwest.com/loyalty/my.../rapid-rewards) a modal dialog box pops up asking for my login information. With the exact same login details (supplied in each case via my login / password manager) I get the error Enter a valid password. on the modal dialog. Clearly there is a flawed password validity script that runs when the login modal dialog is presented, versus when logging in via the non-modal overlay form that is shown when clicking "Log in." This has been an issue for a very, very long time...maybe 12 to 18 months or more, as a WAG?