Checkout failing in a headless store with subscription - store refused to connect

Retired Boards Appdev Custom Storefronts

Topic summary

A headless Shopify store selling subscription-only products is experiencing checkout failures that began this week. The store uses custom apps for Shopify Subscriptions API and Storefront API integration, built with NextJS and launched in September 2021.

Current Issues:

  • Credit card payments failing with error: “store.myshopify.com refused to connect”
  • After entering card details, the thank you page doesn’t appear
  • PayPal and Shop Pay continue working normally
  • Some card orders are still processing successfully, but most fail

Technical Context:

  • Non-Plus Shopify plan
  • No Shopify Scripts or Checkout Extensions in use
  • Custom apps don’t interact directly with checkout
  • Previously functioning without issues since 2021

Support Response:
Shopify support suggested the store has “too many custom apps installed” but couldn’t provide specific troubleshooting guidance.

Status: The issue remains unresolved. The poster is seeking advice from others who may have encountered similar problems or have debugging suggestions.

Summarized with AI on November 23. AI used: claude-sonnet-4-5-20250929.
1

Hi all,

We have a client with a store with only subscription products. For that reason, we developed a custom app with access to Shopify Subscriptions API to handle the selling plan groups, the billing cycle, etc. as per Shopify’s documentation.

Moreover, the web is a headless store, hence we have another custom app just to provide the credentials for the Storefront API used in the headless eCommerce app built with NextJS.

The apps and the store were developed and launched in September 2021.

We use a non-plus Shopify plan.

So far everything goes fine, the headless store creates a cart with the products, we redirect the customer to the checkout, they add the additional info there and then they chose the payment method and pay.

Until this week everything worked fine so far. However, we have started experiencing issues with Shopify Payments.

  • The cards are not working
    • After adding the card details, and processing it the thank you page doesn’t appear and we get a message saying: store.myshopify.com refused to connect.
    • This happens with most of the cards. Altough we can see some orders coming paid by cards.
    • The cards that we tested internally don’t work.
  • Shop pay seems to work.
  • Paypal seems to work.

From Shopify support, they couldn’t help saying that we have too many custom apps installed. However, I don’t see how custom apps can interact with the checkout. At least none of our apps is interacting with the Shopify Checkout. We don’t use Shopify Scripts or any of the Checkout extensions.

Has anyone encountered this issue before, or does have an idea of how to debug it?

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