Installer will not open

Symptom: /install is 404, 403, 500, or already locked.

Likely cause: wrong document root; first admin already exists; PHP error; missing vendor.

Check

1. Document root is backend/public (not the repo root, not backend/). PHP 8.4.
2. storage/logs/laravel.log — uncaught exception vs 404.
3. Whether a platform user already exists. /install is fresh only. It is not an updater.
4. Composer vendor/ present. Missing vendor often looks like 500.

Fix

• Fix the vhost / cPanel document root. Complete Composer.
• If already installed, do not expect /install — 404 is correct.
• Restore from backup if you destroyed the admin user. Never migrate:fresh to “retry” production.

/install does not create cron, a queue worker, or SMTP. After first admin: post-checks.

Escalation: Contact with logs redacted. Never paste APP_KEY.

Related: HTTP 500, Web Installer.