Menu disappears on mobile view

I have just installed a pro plugin that is essential to my site (EasyAzon). The only problem is it is breaking the top men on mobile view for some reason.

When you view my site (www.experttabletennis.com) on a mobile device, or just decrease the browser window on a computer, you see that the mobile menu doesn’t appear when the screen size is small. There is just nothing there.

And ideas how I can fix this? I doubt the EasyAzon plugin people will have many ideas and removing the plugin isn’t really an option as it is key for me generating Amazon affiliate income from my site.

Thank you very much.