Hey! I was also having trouble with this – you just need to change 'min-width' to 'max-width' I think
So – on the website I was designing, the nav links kept going to multiple lines, and I wanted it to just snap to the hamburger/mobile mode earlier
I couldn't get the code provided here to work, until I realised you need to change it to max-width.
On my site, I needed it to switch to mobile mode once it hit 1240px
Hope this helps!