Why can’t I open the hamburger menu on Shopify?
That dialog is actually coming from the Shopify theme editor’s security sandbox it intercepts javascript:void(0) links and shows that warning instead of letting them fire normally. It doesn’t necessarily mean your hamburger menu is broken on your actual store.
First thing to check: open your live storefront in a browser tab (not the editor preview) on a mobile device or with your browser window narrowed, and try the hamburger menu there. There’s a good chance it works fine and the issue is only inside the editor.
If it’s also broken on the live store, the problem is in your theme’s menu toggle code. The hamburger button is likely missing its JavaScript event listener, or the listener isn’t attaching properly. Here’s where to look:
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Go to Online Store → Themes → Edit code
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Look in your theme’s JavaScript files (usually
theme.jsorglobal.js) for the hamburger/mobile menu toggle function -
Check whether the click handler is actually being bound to the menu button element if the selector is wrong or the script loads before the DOM is ready, the button does nothing when clicked
If you’ve recently edited your theme or installed an app that injects code, that’s the most likely cause of the listener breaking. Reverting to a backup of your theme (Shopify keeps them go to Themes → your theme’s “…” menu → Edit code and check “older versions”) is the fastest way to test whether a recent change caused it.
If you haven’t touched the code and it was working before, share which theme you’re using and I can point you to the specific file to check.
What theme you’re using?
Have you made any resent changes?
Can you share a link to your store and preview password if one is set?
Yes, theme editor configurator can be picky in some aspects. Often these blocked things work fine for your online visitors.
Did it ever work in the past?
A quick look at your site shows that there may not be an actual event listener hooked up to the button. I manually wrote a bit of JS and was able to get the mobile menu to trigger, so it’s there, but whatever scripts your theme uses does not have a JS eventListener set up properly to trigger when a user clicks on those icons.
If you made changes to any .js scripts on your theme, it may have caused issues. You can contact your theme developer or reach out and I may be able to help you if you need it! 
I’m using this theme. https://landmark-property.myshopify.com/ , Yes, when I click on mobile, the hamburger menu doesn’t function, and previously I was using a widget for the header banner
I’m using this theme. https://landmark-property.myshopify.com/ , Yes, when I click on mobile, the hamburger menu doesn’t function, and previously I was using a widget for the header banner
To diagnose your problem it is necessary to see your site, which we can not without the password.