FCGI is a module or a protocol, which when used is able to handle more webpage requests at one moment. Not only that, it also improves the performance of applications for web server and it provides much more security. It's known as the replacement of CGI with just a few more extensions.
Without any changes of the configuration in the ticket, meaning that the php's ini @ /etc/php will be used. If you want to use the one of the domain, you have to configure it.
If you are trying to solve it you can look at SysCP - The Open-Source System Control Panel. They were discussing this error too. According to that discussion you have to change from mod_fastcgi to mod_fcgid