Hamburger menu not showing and not functional after update

Good afternoon,

recently I’ve updated one of our websites. It was lagging a fair bit behind.
Wordpress was updated from version 4.9.4 to version 5.6 and the enfold theme was updated from version 3.4.6 to version 4.7.6.4. Sadly after the update the hamburger menu doesn’t appear and isn’t functional in the mobile version of the website anymore, while it does show up in the page source.

I’ve looked around and have read multiple posts that had problems with the hamburger menu but none of their solutions were able to help.

We do use a custom child theme but in the header.php file we call the helper from the parent enfold theme
//fetch the template file that holds the main menu, located in includes/helper-menu-main.php
get_template_part( 'includes/helper', 'main-menu' );

Currently I’m at a loss and I have no clue on how to fix this.