Switched or updated your Shopify theme and the Size Chart or Find my size button is gone? Don't worry — your size charts, quizzes and settings are all intact. Shopify app embeds are theme-specific: when you publish a new theme, it doesn't inherit the old theme's embed settings, so SmartSize starts switched off. Turning it back on takes about two minutes.
Step 1: Check the extension status
From the SmartSize Home page, open the App extensions card and check whether the extension you need is Active on your live theme — the size chart extension for size charts, the fit quiz extension for fit quizzes. If it shows Inactive or mentions a different theme, the app embed wasn't carried over to your new theme.
Step 2: Turn the extension back on in your new theme
Open the Shopify theme editor for your new theme, go to App embeds, find SmartSize, turn the extension on, and save.
Make sure you're editing your live theme — changes saved in a draft or development theme don't affect what shoppers see.
If you enabled the embed in a draft theme, either publish that theme or enable the embed again on the current live one.
Still missing? Try a different placement
Different themes structure their product pages differently, so automatic placement that worked in your old theme may not find the right spot in the new one. If the extension is active but the button still doesn't appear:
Switch to the Floating button — it doesn't depend on your product page structure and works on almost any theme.
Or use App block placement to put the button exactly where you want it in the theme editor.
See Choose where the size chart button appears or How to place your fit quiz button for all placement options. Also worth a glance: if your new theme uses different collections or product types, review your product display rules — the old conditions may no longer match.
Custom or headless themes
If your theme is custom-built, heavily modified, or headless, the standard app embed may not load even when it's turned on. A few things your developer can check:
Whether the theme supports Shopify app embeds at all — some custom setups bypass them, and SmartSize then needs a custom integration.
Whether aggressive theme CSS overrides the popup's styles, making it misaligned or unreadable.
Whether theme JavaScript blocks SmartSize scripts — browser console errors are the giveaway.
If automatic placement can't find the product form, use Custom selector placement with a CSS selector pointing at the exact element.
Check the result
After applying a fix, save everything, open a product page on your live storefront and refresh. Confirm the button appears, clicking it opens the popup, and the popup looks correct — on both desktop and mobile.
If it still doesn't work
Contact SmartSize support and include: your new theme's name, the product URL where SmartSize is missing, screenshots of the App extensions card and the theme editor's App embeds panel, any browser console errors, and whether the theme is custom-built or headless. That's everything we need to pinpoint whether it's an integration, CSS, or JavaScript issue.
💡 Tip: whenever you publish a new theme, take 30 seconds to re-enable the SmartSize app embed before going live — it's theme-specific, so it starts switched off on every new theme.