Network requests fail from deployed store to backend, works locally

App Bridge
1

I’m running into a problem with my Shopify app. Last week everything was working perfectly, but today I can’t make any network requests from my store, only when deployed.

Some details:

  • Both my frontend and backend are deployed to Fly.io.

  • Locally, everything works fine.

  • When I try to make a network request to my Node backend from my local store, nothing happens.

    • I don’t see any errors.

    • The request doesn’t appear in the Network tab of the browser dev tools.

  • I still see console logs up until the point of the request.

  • On the backend, I don’t see any logs for that route.

Here’s the function I’m using to make the request:

  const fetchAppStatus = async () => {

    setLoading(true);

try {

const response = await fetch("/api/app-status");

if (!response.ok) throw new Error("Failed to fetch app status");

const data = await response.json();

    } catch (err) {

showToast(`Error fetching status: ${err.message}`, true);

    } finally {

setLoading(false);

    }

  };
2

Hi @Alija_Fajic

When deployed, if your frontend and backend are on different domains or subdomains, /api/app-status will try to hit the frontend’s domain, not the backend. You’ll want to use an absolute URL or set up a reverse proxy so that /api/app-status routes correctly in production.

3

Hi @Liam-Shopify,

Thank you for your response. That is not the problem, I have also tried with the absolute URL, although my frontend and backend are on the same domain.

I got a suggestion to try this function in the Google console and to execute it there. In the browser, I got this error:

host-B3PrGjK7WOZy.js:18 GET https://myapp.fly.dev/api/auth?shop=undefined 500 (Internal Server Error)

And on the backend I see this:

[shopify-api/ERROR] Missing Authorization header, was the request made with authenticatedFetch? | {isOnline: false}
Session was not valid. Redirecting to /api/auth?shop=undefined | {shop: undefined}
GET /api/carrier-services?shop=myStore 302 1.208 ms
OPTIONS /api/auth?shop=undefined 204 0.147 ms - shop=undefined
No shop provided to redirect to auth

But probably this is happening because in the console, “shop” doesn’t exist.

When i open my application on the Shopify, api for status is called, and on the backend, I only see these logs.

2025-11-26T08:50:32Z app[7816dd0be12528] arn [info]GET /?embedded=1&hmac=fdb1209af9b9cd72906ab&host=YWRtc3RvcmUvbG9ndHJhZGUtdGVzdC1zdG9yZS0y&id_token=oSr4vift9qcRga0&locale=en&session=aab6b1b31726f4fcbec354074784c5237c2f1&shop=myShop.myshopify.com&timestamp=1764147032 200 26.074 ms - shop=myShop.myshopify.com - These are not real values, I edited them

2025-11-26T08:50:32Z app[7816dd0be12528] arn [info]GET /assets/index-DZDU4ZvY.js 200 0.971 ms - shop=-
2025-11-26T08:50:32Z app[2867d55b6e39e8] arn [info]GET /assets/index-DbpU1vhr.css 200 1.009 ms - shop=-
2025-11-26T08:50:32Z app[7816dd0be12528] arn [info]GET /assets/en-C5k7Hynn.js 200 0.847 ms - shop=-
2025-11-26T08:50:32Z app[2867d55b6e39e8] arn [info]GET /assets/en-BQD6kysk.js 200 1.242 ms - shop=-

4

I have created a test endpoint without authentication/authorization

router.get(“/test”, (req, res) => {

res.status(200).send(“Test endpoint is working!”);

});

When I test it from Postman, I get the result.

But when I try from my Admin app:

const testFetch = async () => {
    try {
console.log("Testing fetch to backend");
const response = await fetchWithAuth(`/api/test`);
console.log("Test fetch response:", response);
const data = await response.json();
console.log("Test fetch data:", data);
    } catch (error) {
console.error("Test fetch error:", error);
    }
  };

I have also tried with the full URL → `${BACKEND_BASE_URL}/api/test`
But it is same for both cases. I can’t see the network req in the network tab and in the console I see just this: Testing fetch to backend and nothing more.

When i execute this function from the Google chrome console with absolute URL I got the response.

5

Hi @Liam-Shopify,

I hope you’re doing well. Do you know if anything changed recently on Shopify’s side, perhaps in the latest update, related to tokens, sessions, or security? My frontend suddenly can’t make network requests to my backend, but it can still make requests to other APIs.

I deployed everything again to the new server, but nothing changed.

6

Good news.
When I changed my hosting from Fly.io to Render, everything is working as expected.