Admin Panel Blank After Deploy to App Engine

System Information
  • Strapi Version: 4.1.8
  • Operating System: Google App Engine
  • Database: Postgresql
  • Node Version: Postgresql
  • NPM Version: >=6

After deploying to App Engine, admin panel show loading and show white blank page after that.
Already changing default admin URL by following this Post Setup Documentation, but when I visited /dahsboard , it show json api with 404 error