404 page in Shopify when installing the official template app (cloud hosted)

First, I successfully tested installing the app (using the official template https://github.com/Shopify/shopify-app-template-remix) and running it locally. Preparing for production, I move the app to cloud hosted (Render).

I set up the ENV vars for the app and on the Partner Portal I did set up the corresponding app URL:

https://shopify-app.onrender.com/

and redirect URLs:

When clicking on install the app on a test store, Shopify does two HTTP requests:

GET /?hmac=293349b96e7f4c149e521a22ab1166808469d57f59bec22caca5f285d518c2b2&host=YWRtaW4uc2hvcGlmeS5jb20vc3RvcmUvbmV4YXJhLXRlc3Qtc3RvcmU&shop=nexara-test-store.myshopify.com&timestamp=1741785715 302
GET /app?hmac=293349b96e7f4c149e521a22ab1166808469d57f59bec22caca5f285d518c2b2&host=YWRtaW4uc2hvcGlmeS5jb20vc3RvcmUvbmV4YXJhLXRlc3Qtc3RvcmU&shop=nexara-test-store.myshopify.com&timestamp=1741785715 302

guillem_soler_0-1741793448522.png

And then I see Shopify 404 Error page:

I am doing something wrong or missing something? According to the template docs, OAUTH is already configured, but maybe something is needed so it works.