Your PHP Version is 8.2.26
The correct include statement to include Form.php is the following:
include_once rtrim($_SERVER['DOCUMENT_ROOT'], DIRECTORY_SEPARATOR) . '/phpformbuilder/Form.php';
This is the default path used in all templates. You've got nothing to change.
/var/www/vhosts/anpagrossmarket.com/public_html/phpformbuilder/plugins/
/phpformbuilder/server.php
/var/www/vhosts/anpagrossmarket.com/public_html/phpformbuilder/server.php
/var/www/vhosts/anpagrossmarket.com/public_html
/var/www/vhosts/anpagrossmarket.com/public_html
/var/www/vhosts/anpagrossmarket.com/public_html/phpformbuilder
/var/www/vhosts/anpagrossmarket.com/public_html
https://anpagrossmarket.com/phpformbuilder/plugins/