Could you please deactivate the wpForo plugin (just deactivate, don't click on the Uninstall button) and try the same with some other page? 

Thanks, No I have not added any custom codes and I don´t see any redirection. Do you also see the redirection when accessing the password protected page mentioned above?

Have you added some custom codes in the functions.php file? Please check and make sure there is no redirection code like the following one:

add_filter('wpforo_after_init_current_object', function ($current_object){
    if( in_array($current_object, array('forum', 'topic')) ){
        if( !WPF()->current_userid && !WPF()->perm->forum_can('vf', $current_object) ){
	        wp_redirect( wpforo_login_url() );
	        exit();
        }
    }
    return $current_object;
});

My page https://authentic-self-empowerment.com/ase-supervision-group-session-videos/, which is password protected, is since today being redirected to our forum sign in page: https://authentic-self-empowerment.com/ase-supervision-group-forum/?foro=signin

See screenshot attached. I have not made any changes and am trying to figure out what might have happened and how to get the page back to the version where it displays the field to type in a password.

Any idea of what might have caused this would be most helpful and appreciated.