In my react app I have my variable

const BACKEND_URL = "https://

In my backend for testing I put CORS(app, resources={r"/*": {"origins": "*"}})

However, when I run my already deployed app I get this error

Mixed Content: The page at 'https://mysite/route was loaded over HTTPS, but requested an insecure resource 'http://urlbakend/route/'. This request has been blocked; the content must be served over HTTPS.

I don't understand why http appears when my app is https

And on the network it appears Referrer Policy:

strict-origin-when-cross-origin

I don't know what else I've done, I have everything here in railwai in a project