This is expected. Functions are handled by CLI which is running on :8888. Your application is running on :3999 which doesn’t know about Netlify Functions. Visit the Function on http://localhost:8888/.netlify/functions/hello
yes, with this link it’s working and it’s working also the form on the main page.
However if i upload the file to Netlify and i try to complete the form, it doesn’t work and i get this on the console “Failed to load resource: the server responded with a status of 404 ()”