When retrieving License Keys on Tools & Settings > License Management > Retrieve Keys below error is displayed in the browser:
CONFIG_TEXT: 502 - Web server received an invalid response while acting as a gateway or proxy server
CONFIG_TEXT: This site can't be reached ERR_RESPONSE_HEADER_TOO_BIG
CONFIG_TEXT: [error] 27895#0: *5468586 upstream sent too big header while reading response header from upstream
#PPPM-11672 "Retrieving keys now works correctly (a 502 Bad Gateway error is no longer shown) on servers with a large number of customers, resellers, or additional users (more than 700)."
- Plesk Obsidian 17 March 2020
As a workaround:
Connect to the server via SSH.
Open the file
/etc/sw-cp-server/configand change the following parameters as below:
CONFIG_TEXT: fastcgi_buffers 64 128k;
Restart sw-cp-server and sw-engine services:
# service sw-cp-server restart && service sw-engine restart
Retrieve key in Tools & Settings > License Management.
If steps above did not help, run:
# plesk bin license --retrieve