504 Gateway Time-out nginx/1.18.0

Hello

i use nginx and apache2 with php fpm but i got this
504 Gateway Time-out
nginx/1.18.0
how to fix it ?

make sure all of the services are running, and ports are configured appropriately

systemctl status nginx
systemctl status php-fpm
systemctl status httpd
//Below are possibly used/notused//   " systemctl " by itself will list all services
systemctl status php72-php-fpm << If that's what the user account is setup to use

okey i resolve it but now i got RELAY HOST DENIED when a send mail to my postfix server

okey i resolve it but now i got RELAY HOST DENIED when a send mail to my postfix server

Relay Host Denied usually means your not logging in before sending the header info.  How exactly are you sending to postfix.