@camilatigre here's a few recommendations and how to fix the sign-in request:

• (recommendation) Change the repository's visibility to private.
• (recommendation) Rename src/api/api.jsx to src/api/api.js).
  The extension .jsx should be used for UI components only.
• (recommendation) On src/api/api.js:11, loose the request header Access-Control-Allow-Origin.
  That's a response header only and has no effect when sent on a request.
• On src/api/api.js:13, rename the property data to body.
  That's the correct name for the body payload property.

Signing in should work after those changes.

const baseUrl = "http://api.staging.pagtree.31.220.53.245.nip.io:4000"

const response = await fetch(`${baseUrl}/_private/auth/sign-in`, {
    method: 'POST',
    headers: {
      'Accept': 'application/json',
      'Content-Type': 'application/json'
    },
    body: JSON.stringify(credentials),
  });