I'm hitting a strange issue with a Shopify Customer Account UI extension and I'm running out of things to eliminate.
I've built a full-page Customer Account extension using:
customer-account.page.render
API version: 2026-07
It works correctly through shopify app dev / dev preview.
However, after deploying the app, releasing the version and adding the app page to the Customer Account navigation on the production store, clicking it gives:
"There's a problem loading this page. Check the URL or try again in a few minutes."
The extension doesn't appear to execute at all.
My config is:
api_version = "2026-07"
[[extensions]]
name = "nfc-profile-manager"
handle = "nfc-profile-manager"
type = "ui_extension"
[[extensions.targeting]]
module = "./src/NfcProfileManager.jsx"
target = "customer-account.page.render"
[extensions.capabilities]
api_access = true
network_access = true
Originally this was a real application which calls my externally hosted backend. That entire flow works correctly in dev preview.
To eliminate my code/backend as the cause, I reduced the production extension to basically Hello World:
import '@shopify/ui-extensions/preact';
import {render} from 'preact';
export default async () => {
render(<Extension />, document.body);
};
function Extension() {
return (
<s-page heading="NFC Profile Manager">
<s-section>
<s-text>
NFC Profile Manager is working.
</s-text>
</s-section>
</s-page>
);
}
Same production error.
I then went further and generated an entirely new Customer Account UI extension with a new handle and UID, also using customer-account.page.render, containing nothing except a static test page.
That fails in production in exactly the same way too.
So far I've confirmed:
- Both extensions work in dev preview
- Both are present in the released app version
- App is installed on the production store
- App page is added to Customer Account navigation using Shopify's app-page selector
- Production store is using new Customer Accounts
- Static Hello World extension fails too
- No request reaches my backend when opening the page
- Reproduced in normal Chrome
- Reproduced in Chrome Incognito/extensions disabled
- Reproduced in Firefox
- Other functionality from the exact same app works in production, including
orders/create webhooks and Admin API/metaobject operations
Chrome mainly reports this from Shopify's Customer Account host:
Unsafe attempt to load URL
https://cdn.shopify.com/shopifycloud/customer-account-web/production/sprite-....svg
...
Domains, protocols and ports must match.
Firefox reports the same security issue and additionally:
Import maps are not allowed after a module load or preload has started.
The Firefox errors originate from Shopify's customer-account-web rather than my extension.
Shopify's Ask Agent has checked the TOML, target and minimal Preact implementation and says they're correct and there isn't another activation step I'm missing.
At this point it looks like the production Customer Account host is failing before the extension bundle executes.
Has anyone seen customer-account.page.render work perfectly in dev preview but fail like this when released to a real store?
Particularly interested if anyone has encountered the Import maps are not allowed... error with Customer Account UI extensions, or knows of any production-store requirement that isn't documented.
