admin-url-cookie-path

Cookie path must match

When you change url, you must also update auth.cookie.path to the same value. The cookie path defaults to '/admin' regardless of url, so if they differ, the browser will not send the authentication cookie to the new path and logins will silently fail.

/config/admin.js

module.exports = ({ env }) => ({
  url: "/dashboard",
  auth: {
    cookie: {
      path: "/dashboard", // must match url
    },
  },
});

After changing auth.cookie.path, rebuild the admin panel before starting Strapi, as this value is inlined into the admin bundle at build time.