There's another community post with 404 debugging tips that might be helpful. Please give these solutions a try and let us know how it goes.

https://community.vercel.com/t/debugging-404-errors/437

Vercel Community

Debugging 404 Errors

Sometimes things don’t go as expected when deploying a website. If you see a 404 on your site, that means the page or resource couldn’t be found. There are...

A human should be around soon to offer more advice. But you can also get helpful information quickly by asking v0.

Hi @divyalaldinani-gmail, welcome to the Vercel Community!

It seems like you've set up the root directory correctly. You should also set the Framework preset to Next.js:

Reploying after this change should solve the issue.