Troubleshooting

Use this page when the widget is missing, add-to-cart fails, or checkout does not show the bundle discount. For Tapcart-only steps see Tapcart.

Checklist

Knit is installed and has been opened once in Shopify admin.
The bundle is Active and includes the product you are testing.
In Shopify admin → Discounts, the Knit automatic discount is Active.
You are testing a product that actually belongs to that bundle (product match or collection membership).
You waited up to 5 minutes after the last bundle edit (cache).

Symptom	Likely cause	What to do
Blank on a Liquid product page	Theme app extension not enabled, or product not in an active bundle	Enable the app embed in the theme editor. Confirm the bundle is Active and includes this product.
Blank iframe (headless / Tapcart)	Wrong `shop` domain, or embed origin blocked	Use `{store}.myshopify.com`. If the console says refused to connect, the host must allow `https://app.knit-bundle.co`.
”No bundle” / empty widget	No matching active bundle	Add the product (or its collection) to an Active bundle.
Headless JSON `APP_NOT_INSTALLED`	Storefront token not provisioned	Open Knit once in Shopify admin, then retry.
Headless JSON `INVALID_PARAMS`	Missing or invalid `shop`	Pass `shop=your-store.myshopify.com`.
Headless JSON `NOT_FOUND`	Headless not enabled on this deployment	Contact Knit support.
Stale products or old tiers	Cache	Wait up to 5 minutes, then reload.

On Liquid: confirm the theme is not intercepting the widget button, and that ATC override is only on if you intend the theme button to add the bundle. See Shopify integration.
On headless: you must handle addToCart over postMessage and reply with addToCartResult within about 10 seconds, or the widget shows CART_TIMEOUT. See Headless Bundles API.
On Tapcart: publish the app after adding the block, then test on a device, not only the static canvas.

Items can land in the cart at full price when __FB_ATC_UID never reaches Shopify.

Confirm the Knit automatic discount is Active.
Confirm the bundle is Active.
Inspect the cart or order: each bundle line must show __FB_ATC_UID as a line-item property.
If a cart app, Hydrogen cart, or middleware strips custom properties, keep this one. See How discounts apply.

Include:

Shopify domain (your-store.myshopify.com)
Product handle or ID
Endpoint URL or page URL
Full JSON error ({ ok: false, code, message }) or [nameless] / [knit-bundle] console logs
Screenshot or recording (storefront, Tapcart preview, or device)