Custom breakpoint for a Site Header Menu element

Hi,

I am really struggling to get a Menu Element in a Site Header that I created, to switch to a Hamburger Menu at a certain breakpoint.

Because the Menu Items are many I am trying to switch the Menu to a Hamburger Menu at a fairly high breakpoint; 1700 pixels Viewport width.

I discovered that the Customizer’s Breakpoint setting doesn’t really affect a GB Pro Site Header element.

I have tried to follow two of your answers to others with a similar problem, but the CSS I write has no effect.

Can you help me? If you want to take a look at the Site Header in the question, go to the URL I have provided in the Private Information section. It’s a Global Site Header that I have bulit using the Site Header element.

Many thanks

BW Peter