OAuth2 returns 'No input file specified' error when authorizing a Microsoft 365 mailbox on Apache with mod_fcgid

Ensure Apache mod_rewrite is installed and enabled, and that AllowOverride All is set in the Directory block for the osTicket root. Add [R,L] to the RewriteRule in api/.htaccess and reload Apache. If it still redirects to the homepage, a PHP error is occurring silently -- enable display_errors = 1 in bootstrap.php temporarily and check PHP and Apache error logs. Common causes: URL rewriting misconfiguration, wrong redirect URI in the Azure app registration (must exactly match the osTicket OAuth2 callback URL), or PHP-FPM socket permissions.