If this error causes your entire site to be unavailable, go to wp-admin > Plugins
and temporarily disable the WP Staging plugin until we fix the issue.
wp-content/plugins/wp-staging(-pro)
with FTP to disable the WP Staging plugin.#0 /var/www/html/wp-config.php(86): require_once() #1 /var/www/html/wp-load.php(50): require_once('/var/www/html/w...') #2 /var/www/html/wp-blog-header.php(13): require_once('/var/www/html/w...') #3 /var/www/html/index.php(17): require('/var/www/html/w...') #4 {main}