In the linked page above you describe how to solve it. Is that functions.php code still working or we need to use another one? Or do you improved your compatiblity out of the box with ERP system JTL out of the box?
Please, disable all plugins that are not related to our theme and provide us with your admin access. We will log in and check what is wrong there. You can leave only the following plugins that are required for our theme:
WoodMart core
WooCommerce
Elementor/WPBakery page builder