Getting error message setting up Pro Sites Plugin

Trying to install the plugin Pro Sites. Been looking over the past discussions and it seems like or maybe not that I might miss out a step.

I have this Error Message.

Plugin could not be activated because it triggered a fatal error.
Fatal error: Call to undefined function switch_to_blog() in /home/devunmeo/public_html/wp-content/plugins/pro-sites/pro-sites.php on line 193

I installed it by uploading it through FTP.

Working on Wordpress 3.4.1 with the default theme.

any suggestions?

Thanks