Accessing Password-Protected Pages and Error Handling

A community member's pages are password-protected. When someone enters the wrong password, an error message appears. However, if they try to access the page without entering anything and click the button, they are redirected to a 404 page. The community member would like to display an error message instead. Another community member suggests using the "Users" functionality or Memberstack/Outseta as a possible solution, but there is no explicitly marked answer.