Hello there,
Do you properly arrange the menu in Appearance-> Menu because when I am testing this theme all menu level work fine.
Yes I did. I disables all plugins and still only the first level works
The causing the problem is the child theme. If I use the theme and not a child theme it works fine. I removed the child them, created a new child theme without anything it except a style.css with nothing specified except the header and function.php nothing specified in that file either and the second menu level doesn’t work. Any thoughts?