Website displays an error 502: AH01075: Error dispatching request to : (polling)

Symptoms

• example.com website shows
502 Bad Gateway error.
• The following error is recorded in Domains > example.com > Logs or in /var/www/vhosts/example.com/logs/error_log file when reproducing the issue:

AH01075: Error dispatching request to : (polling)

Cause

Website's PHP code is taking too long to execute and exceeds the timeout limit.

Resolution

Increase the PHP timeout limits:

1. Log in to Plesk

2. Add the following lines to Domains > example.com > PHP Settings > Additional configuration directives:

fastcgi_send_timeout 120s;
fastcgi_read_timeout 120s;

Or increase the values if they are already configured