Nav menu disappears on mobiles

Hello,

I am using a child theme of miniamaze, which I love.

Having a big issue though since my navigation menu doesn’t show on mobiles (not sure at what width it disappears). I’ve seen in your demo that the nav menu is responsive, even if you reduce the width the pages appear and if it becomes too narrow a darker area with menu symbol (three lines) appear. Well this doesn’t happen at all with my website, I don’t know why and I can’t see how to fix it.

My website is: https://www.acuhealth.org.uk

I tried amended the code as on style-responsive.css and it didn’t work

I have checked and the menu appears now on some tablets but if I reduce the width, the menu disappears and the dark area with menu symbol doesn’t appear.

Can anyone shed light on this, please?

Thanks, A.