Navigation Menu Showing as Mobile Menu after Update

Hello, I've recently updated to Bold Photography 1.2, however, I am using my existing child theme which was based on the previous version. This was automatically updated so I didn't get a chance to catch it before the update, but it's caused a major problem. As far as I can see the site works just fine in all aspects, apart from one key issue. The menu is now not showing as a nav bar, it's showing as the mobile version on desktop. It's nothing to do with my screen size - I'm running full screen on a 5K iMac, in addition, the menu doesn't work. You just click and nothing happens. What's even weirder is that when I'm logged into WordPress as admin, the site looks and works fine. This is how it looks for me, all fine and dandy This is how users are seeing it, cross-platform The web address is: So far I've tried the following to no avail:

• Clearing cache on Autoptimise & WPFastest
• Updating all plugins, themes and wordpress version

Anyone on here able to offer some support? I don't think it's a wordpress issue. Any support much appreciated!