Shopify size chart / fit guide popup not opening — theme JS, metafields, app block.

Several products can look like “the product-page button is broken.” They do not share a settings panel. This page is only when the Size chart / Fit guide / Sizing guide control is missing, does nothing on click, or the popup / modal / dialog never opens on the product page. A dead heart / wishlist / save for later control is wishlist button not working. A stuck product variant picker or swatches UI is variant picker / swatches not updating. A blank Judge.me / Loox / Okendo reviews widget is product reviews not showing. A stale cart drawer after a successful add is cart drawer / AJAX cart not updating. This page is only: size chart / fit guide popup on the product page.

Seven ordinary reasons the popup stays closed: theme product JS / dialog custom element unbound after a theme publish, size-chart metafields empty or pointing at the wrong page, product template missing the size-chart app block, app embed disabled on the live theme, CSS pointer-events:none or display:none on the trigger, two size-chart / fit-guide apps fighting the same open handler, or you are debugging wishlist / variant picker / product reviews / cart drawer instead. Walk them in that order. You already pay for the theme or size-chart app. You do not need another seat to make a Size chart link that already exists open a modal.

Pick a published product that should show a size chart. Open the live product page in an incognito window. Click Size chart / Fit guide / Sizing guide. Screenshot whether a dialog, details drawer, or modal mounts; whether the URL hash / query changes; and whether focus moves into the popup. Open Theme editor on the live theme → product template and note whether a size-chart / fit-guide block or custom liquid section is present. Open the product admin → Metafields and confirm the chart table, rich text, or page reference has values. Open DevTools → Console / Network for uncaught errors and any size-chart app endpoint.

Honest proof: if the metafield / page has content and the click still never opens a surface, stay on this page — that is theme JS, app blocks, or conflicts. If the heart / wishlist never toggles, leave this page for wishlist button not working. If option clicks leave price / image stuck, use variant picker / swatches not updating. If the reviews section is blank, use product reviews not showing. If Add to cart works but the cart drawer stays stale, use cart drawer / AJAX cart not updating. Do not mix those proofs.

Dawn-family and most OS 2.0 themes open size charts with a native <dialog>, <details>, or a custom element wired in the product section JS. A theme switch, section reorder, “reset sections,” or a customizer edit that drops the trigger button’s data- attributes / aria-controls is the most common “Size chart does nothing” ticket — the chart content may still exist in metafields; the open listener is gone.

Fix: Theme editor → product template — confirm the Size chart / Fit guide trigger and its matching modal / drawer section are both present. Compare against an unmodified Dawn product section if you forked heavily. Check console for custom-element upgrade failures after the product form re-renders (variant change often re-mounts the form and orphans listeners). Variant media and combined-listings UI bugs still belong on variant picker / swatches not updating— that is product options, not the size-chart modal.

Many themes and size-chart apps render the popup from a product or variant metafield (rich text / table / file) or a page reference metafield. When the definition exists but the product has no value, the trigger may still render and open an empty shell — or the theme hides the trigger entirely when the metafield is blank, which looks like “the Size chart link is gone.” Wrong namespace after a migration (custom → app-owned) is the same symptom on every product.

Fix: Products → open one SKU → Metafields — fill the size-chart / fit-guide field the theme or app expects. If the theme reads a page, create / publish that page and link it. Spot-check 3 products across sizes. Wishlist apps that write customer metafields are still wishlist button not working— different surface from a product size-chart metafield the modal reads.

Online Store 2.0 themes mount size-chart / fit-guide apps through an app embed (global script) and one or more theme app blocks on the product template (Size chart button, fit guide drawer, chart table). A theme switch, duplicate, or “reset sections” publish that drops those blocks is a common “fit guide disappeared” ticket — the app is still installed; the storefront slot is gone.

Fix: Theme editor → App embeds — enable the size-chart / fit-guide app on the live theme and Save. Product template — add / re-enable the Size chart / Fit guide blocks near the variant picker or ATC, Save. Preview then hard-refresh the live product URL. Product reviews app blocks are still product reviews not showing— this page is size chart / fit guide, not stars.

Stores that migrated from one size-chart / fit-guide app to another often leave the old app embed, leftover liquid snippets, or a custom “Size guide” button that preventDefaults the new app’s listener. Custom CSS that sets pointer-events:none, overflow:hidden on body without a matching open class, or z-index under the sticky ATC also looks like “the popup never opens.”

Fix: keep one size-chart owner. Disable the old app embed and remove orphan liquid / sections on a development theme first. Check console for uncaught errors when the product page loads and when you click Size chart. Search theme CSS for size-chart / fit-guide class hides. Cart drawer Section API bugs after add-to-cart are still cart drawer / AJAX cart not updating— different surface from a dead size-chart modal open.

A dead wishlist / save for later button is wishlist button not working. Stuck product variant picker / swatches is variant picker / swatches not updating. A blank product reviews widget is product reviews not showing. Stale cart drawer / AJAX cart after add is cart drawer / AJAX cart not updating.

The only honest test for this page: a published product’s Size chart / Fit guide control appears on the live product template, metafield or page content exists, theme JS / dialog binds, app embed and product template blocks are on if you use an app, only one size-chart owner is installed, console is clean on click, and the popup / modal / drawer opens with the chart visible. Anything else is a different product.

Stay DIY if you can spend one afternoon on the list above: prove click vs modal open, re-bind theme product JS / dialog sections, fill size-chart metafields or page references, enable app embed and product template app blocks on the live theme, and remove competing size-chart apps or CSS hides. That is the whole playbook. No agency required. Short answers also live on the merchant FAQ. Related pages: wishlist button not working, variant picker / swatches not updating, product reviews not showing, cart drawer / AJAX cart not updating.

Pay for help when the work is not the size-chart toggle — it is connecting the stack you already have so lead capture is not dying in DMs, storefront and checkout-ready exceptions land in a channel you already check, and the live store is one workflow instead of a spreadsheet plus a Slack bot you forgot. That is the Latch AI Ops install.

What $997 USD one-time buys: lead capture on the live store, ops alerts in a channel you already check, and a checkout-ready workflow. 72 hours after collaborator access, not after payment. One live Shopify store. Access plus a delivery thread. Store URL collected at checkout. Not a SaaS seat, not a theme rebuild retainer, not a conversion guarantee, not a brand or theme job.

Other shops’ public ranges, not testimonials: a checkout / ops install typically runs $500–$2,500. A full ops consulting block typically runs $2,000–$5,000. $997 is the cheap end of that work, sold as a 72-hour install of three systems — not as an earnings number or conversion-lift claim.

What it does not buy: more orders, recovered revenue, perfect size-chart popups forever, or a case study. Latch AI Ops has not published customer proof because there are no customers yet. You are buying the install.

Checkout is on Whop. Operator is Nico. United States offer. You can revoke collaborator access after handoff. We do not take owner passwords.