The problem is solved now, because php-fpm is misconfigured at /etc/nginx/sites-enabled/fusionpbx.
Update the Nginx Configuration Edit the Nginx configuration file to point to the correct PHP-FPM socket:
replace fastcgi_pass unix:/var/run/php/php8.1-fpm.sock; with fastcgi_pass unix:/var/run/php/php8.2-fpm.sock;