This article covers methods to fix Plesk error, FPM initialization failed.
Basically, the error "FPM initialization failed" triggers in Plesk mainly in different formats. The is as a result of Incorrect PHP configuration file was generated during subdomain creation via XML API.
To fix this Plesk error:
i. Log in to Plesk server via SSH.
ii. Remove the excessive configuration file:
rm -f /etc/php-fpm.d/subdomain.example.com.conf