The problem was in Google Cloud's CORS, try setting cors.json to the following code:

[
  {
    "origin": ["*"],
    "method": ["GET"],
    "maxAgeSeconds": 3600
  }
]

I had difficulty changing CORS, directly in the Google Cloud console it didn't work, I had to download a tool called firebase admin, create a node project, download the json key from my firebase and run this code:

const admin = require('firebase-admin');

// Inicialize o Firebase Admin SDK com a chave privada
const serviceAccount = require('./comprasnozapkey.json'); // Substitua pelo nome do seu arquivo de chave

admin.initializeApp({
  credential: admin.credential.cert(serviceAccount),
  storageBucket: 'gs://yourbucket',  // Substitua pelo nome do seu bucket
});

const bucket = admin.storage().bucket();

const corsConfig = [
  {
    origin: ['*'], // Substitua "*" pelo domínio do seu app para maior segurança
    method: ['GET'],
    maxAgeSeconds: 3600,
  },
];

bucket.setCorsConfiguration(corsConfig)
  .then(() => {
    console.log('Configuração de CORS aplicada com sucesso!');
  })
  .catch((err) => {
    console.error('Erro ao configurar CORS:', err);
  });

you have to have node npm, you have to have firebase sdk and firebase admin sdk.

I don't remember exactly what the commands were but I remember that I just ran this code. Another quick but not recommended alternative that I found was to use the HTML renderer, but it is slow and not worth it for anyone who is actually creating a website, just for testing, etc. To use the renderer, just use this command in the terminal:

for run:

flutter run -d chrome --web-renderer html

for build:

flutter build web --release --web-renderer=html

Translate the commented lines into Brazilian Portuguese, as I am Brazilian, thanks