Nextjs deployed on Vercel = blank page - reactjs

Question

I managed to deploy my Nextjs app (whith getStaticProps + i18n + firebase) on Vercel.
But i get a blank screen.
Here's the log:
Status: 200
Duration: 8.18ms
Memory Used: 111 MB
I tried :
Checking the build function locally: it works perfectly.
Changing the default build and development settings to these (with no luck) :
I even tried to deploy on netlify (even thought i don't think they support i18n because i18n doesn't support next export), but i get a 404 page, which is the equivalent of a blank page in Vercel.
I also tried:
Creating a new git and re-deploying. But I still get an empty result after a perfect deploy with a list of all my pages and stuff...
Deleting i18n.
Deleting index.html from public
Deleting all pages but one.
Deleting _document.jsx
Deleting every public folder pages except assets like images.
Deleting package lock file.
Stil nothing works.
And yet, i get a perfect previw of my webapp in Vercel, but the link goes to a blank page.
Any idea?

Answer 1

My mistake.
It was a problem with my getServerSideProps code
To this :
export async function getServerSideProps({ req, res }) {
const data = cookie.parse(req ? req.headers.cookie || "" : document.cookie);
if (res) {
if (Object.keys(data).length === 0 && data.constructor === Object) {
res.end();
}
}
return {
props: { userId: data.userId }, // will be passed to the page component as props
};
}
I went to this:
export async function getServerSideProps({ req, res }) {
const data = cookie.parse(req ? req.headers.cookie || "" : document.cookie);
return {
props: { userId: data.userId }, // will be passed to the page component as props
};
}
The res.end(); was the problem.

Answer 2

Deleting the following worked for me:
"homepage": "https://your-username.github.io/the-repo-project/",
vercel --prod
You have to wait a minute
But I think it depends on the project.

Answer 3

I ran into the same issue of having a blank page. I later discovered that I was running "npm run dev" in the wrong directory.
Instead of cd C:\wamp\www\projectname, I typed cd c:\wamp\www\projectname.
The difference is capital letter "C". Small letter "c" won't work.
Ensure your casing (capital or small) is right and everything spelt correctly. Then, run "npm run dev" and see your expected page display (if there are no other errors hindering it from showing).