Burger icon does not seem to be working on mobile device

Hello everyone! There seem to be some issue with burger icon on mobile devices www.slash.com/

Can anyone help me fixing it please?

Here is my site Read-Only: LINK
(how to share your site Read-Only link)

Can you share a read only link?
Have you checked that nothing overlaps your menu link? Try to play with z-index.
What happens when you manually open the menu, can you see it?