Getting a 404 when deploying to Vercel

I get a 404 when deploying to Vercel. But was advised along the way to delete index.tsx I guess it has something to do with:
https://docs.plasmic.app/learn/nextjs-quickstart/#auto-load-all-plasmic-pages

So in /pages I only have :

[[...catchall]].tsx
_App.tsx 
plasmic-host.tsx

What do I do?

OK I think I see now. @icaro wanted me to put my project on Vercel so he can help with an issue.
I followed this and configured my project to point to:
https://plasmic-poc-lincatmerkle.vercel.app/plasmic-host

But still see a 404.

I don’t understand the term Header or Payload? The docs seem to indicate that it’s optional:
https://docs.plasmic.app/learn/publishing/#continuous-deployment-with-webhooks

So I need to run the build script before deploying to Vercel?

Fix with help from @icaro