I see a blank page or a 500 error

1. Open storage/logs/laravel.log and read the last error. It names the file and the reason.
2. Check that storage and bootstrap/cache are writable by the web user.
3. Check the PHP version (8.2 or newer) and the required extensions in Settings > System Information or the installer's requirements page.
4. After editing .env, run php artisan optimize:clear.
5. If the page is blank only in the admin, open System > System Health from another page and fix what it flags.

If the site shows a 500 right after an update, see Troubleshooting.