How to host flutter on firebase?

I am following the steps to host my flutter helloworld application. All steps go smooth, however instead of my application I see this screen.

What can be wrong?

My commands:

polinach-macbookpro3:my_app1 polinach$ flutter build web

💪 Building with sound null safety 💪

Compiling lib/main.dart for the Web...                             391ms
polinach-macbookpro3:my_app1 polinach$ firebase init hosting

     ######## #### ########  ######## ########     ###     ######  ########
     ##        ##  ##     ## ##       ##     ##  ##   ##  ##       ##
     ######    ##  ########  ######   ########  #########  ######  ######
     ##        ##  ##    ##  ##       ##     ## ##     ##       ## ##
     ##       #### ##     ## ######## ########  ##     ##  ######  ########

You're about to initialize a Firebase project in this directory:

  /Users/polinach/_/__/my_app1


=== Project Setup

First, let's associate this project directory with a Firebase project.
You can create multiple project aliases by running firebase use --add, 
but for now we'll just set up a default project.

? Please select an option: Create a new project
i  If you want to create a project in a Google Cloud organization or folder, please use "firebase projects:create" instead, and return to this command when you've created the project.
? Please specify a unique project id (warning: cannot be modified afterward) [6-30 characters]:
 polina-test2
? What would you like to call your project? (defaults to your project ID) 
✔ Creating Google Cloud Platform project
✔ Adding Firebase resources to Google Cloud Platform project

🎉🎉🎉 Your Firebase project is ready! 🎉🎉🎉

Project information:
   - Project ID: polina-test2
   - Project Name: polina-test2

Firebase console is available at
https://console.firebase.google.com/project/polina-test2/overview
i  Using project polina-test2 (polina-test2)

=== Hosting Setup

Your public directory is the folder (relative to your project directory) that
will contain Hosting assets to be uploaded with firebase deploy. If you
have a build process for your assets, use your build's output directory.

? What do you want to use as your public directory? build/web
? Configure as a single-page app (rewrite all urls to /index.html)? Yes
? Set up automatic builds and deploys with GitHub? No
? File build/web/index.html already exists. Overwrite? Yes
✔  Wrote build/web/index.html

i  Writing configuration info to firebase.json...
i  Writing project information to .firebaserc...

✔  Firebase initialization complete!
polinach-macbookpro3:my_app1 polinach$ firebase deploy --only hosting

=== Deploying to 'polina-test2'...

i  deploying hosting
i  hosting[polina-test2]: beginning deploy...
i  hosting[polina-test2]: found 21 files in build/web
✔  hosting[polina-test2]: file upload complete
i  hosting[polina-test2]: finalizing version...
✔  hosting[polina-test2]: version finalized
i  hosting[polina-test2]: releasing new version...
✔  hosting[polina-test2]: release complete

✔  Deploy complete!

Project Console: https://console.firebase.google.com/project/polina-test2/overview
Hosting URL: https://polina-test2.web.app