Keystatic Admin Page - 404 on vercel production deployment

[muddassirhq]

Thankyou @simonswiss and team, Keystatic is a boon for static websites. I was using Keystatic happily in local mode, however, I needed to access my website remotely, so I switched to GitHub mode. I successfully ran and used GitHub mode in dev environment, but when deployed, the Keystatic login page appears, but on login, the page goes 404. My deployment service is Vercel, and I am using Vercel adapter in my Astro.js project.

before login 👆

after login 👆

Please help me fix this, I searched and tried all that was possible, but nothing worked.

I have ensured:

1. .env keys in Vercel
2. correct callback url in GitHub app
3. correct config in Keystatic and Astro.js configs

Btw I often get a blank white page on http://localhost:4321/keystatic but it fixes after re runs or after sometime