Add this css too and delete cache:

@media screen and (max-width: 860px) {
    .page-id-158 #mobile-bar{z-index: 0;}
}

Thank you for all your help! That worked, but also disabled the menu, so the author worked on the code and managed to put the login where the RSS feed logo is, which is hidden if the message is too long. 

Perhaps in the next version of WP-Foro, you might consider putting the login centered in the middle of the page so that no one else has issues logging in?

Thank you again 🙂