Thanks for updating the thread.
I checked the website and after doing the troubleshooting I noticed that the mobile menu is not working because of the CSS codes that’s added in Theme Options > CSS. When I removed the CSS, mobile menu is working fine. Please see screencast.
So, there’s some CSS code that’s affecting the functioning of mobile menu. Please inspect the CSS code and narrow down the code that’s affecting the mobile menu.
Unfortunately, we won’t be able to provide support for custom codes as that falls outside the scope of support we can offer. You will have to narrow down the CSS code either by elimination method or if you are comfortable with Chrome or Firefox dev tools you can easily trackdown the code causing problem.
Here’s resource to get started with dev tools: