Hi. Duplicate of elements IDs on one page are not acceptable. This is the reason for your problem. Remove the section that you use for mobile header and use the standard Header + CSS for mobile adaptation if need.

Hello Jamie Ranston

I have checked your site and it is working fine now. Maybe you have found the solution. Also, thanks to Pavel.

Best regards

The off canvas shows but the menu dropdown isnt working, it works fine on tablet, just not working on mobile

Apology for the inconvenience. Please share your administrator access here to check the issue. Use the Hidden Content box to share the credentials. Make sure that you have a full site backup with you before sharing.

Hi. Template options > Layout tab > Header settings > Responsive > turn ON for all devices.

Or use CSS if Header is predefined (from Template options > Basic tab > Header)

#sp-header {
    display: block !important;
}

About custom css