Language name doesn’t show up

I activated the language menu but the language names don’t show up. English and Spanish are correctly defined at Settings > WP Multilang > Languages and the menu exists, but is empty and therefor invisible to visitors.

Here’s the HTML code showing up in the menu:

<li id="menu-item-language-en" class="wpm-languages menu-item menu-item-type-custom menu-item-object-custom active-language menu-item-language-en"><a href="#"></a></li>
<li id="menu-item-language-es" class="wpm-languages menu-item menu-item-type-custom menu-item-object-custom menu-item-language-es"><a href="https://teatronika.org/el-show/"></a></li>

The page I need help with: [log in to see the link]