App Proxy 500 error: There was an error in the third-party application.

Store Design
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1

Hello, I am having issues querying my app proxy from my storefront App Theme Extension. Every time I query my app proxy URL I received a 500 error and HTML code that says “There was an error in the third-party application.” I have confirmed that my App proxy is not receiving the request because it is producing no console logging. This is my app proxy configuration:

Subpath prefix: apps

Subpath: prapp

Proxy URL: <Tunnel name>/get

App Proxy endpoint: /get/stores

Request URL: [https://<Store](https://<Store) name>.myshopify.com/apps/prapp/stores

This is my app extension code:

const fetchOptions = {
        method: "GET",
        headers: {
          "Content-Type": "application/json",
        },
      };

      return fetch("/apps/prapp/stores", fetchOptions);

I set up and ran the Product Reviews app extension sample project, and I got it to work. I am trying to do the same thing with my own app and Im not sure what I am missing. Is anyone able to provide any insight into this?

2

There is a whole long thread about this error here: https://community.shopify.com/c/shopify-apis-and-sdks/application-proxy-there-was-an-error-in-the-third-party/td-p/529794

3

For whoever is having the issue “There was an error in the third-party application.” with status 500 and requests not reaching their deployment - please check your app proxy URL in the app settings (admin panel, open app, three dots on the right, manage app, app proxy).

When I deployed my app, I installed it to the same store as my development app, that had already occupied the same proxy URL, so shopify appended a number to the new one: “apps/my-proxy-1”. The part of the app that was calling the app proxy was calling the development version of the app proxy.

Simply install your prod app to a different development store or rename the proxies in that case.

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