NGINX PHP-FPM (FastCGI) 504 Gateway Timeout error on

Increase PHP maximum execution time in /etc/php.ini:

max_execution_time = 300

Increase PHP-FPM request terminate timeout in the pool configuration (/etc/php/7.2/fpm/pool.d/www.conf): 

request_terminate_timeout = 300

Increase Nginx FastCGI read timeout  under the http section (/etc/nginx/nginx.conf or /etc/nginx/sites-available/nameofvirtualhost): 

fastcgi_read_timeout 300;