Market Press Install Error

Hello,

Just signed up for your service to install and test the new market press plugin and have run into an error right after installing it. Not sure what I did wrong but I'm pretty discouraged to say the least.

Here's the error I got...

Fatal error: Call to undefined function is_site_admin() in /home/content/g/i/l/giles10/html/MassageAdvantage.com/wp-content/plugins/1289004545-14212/update-notifications.php on line 417

I really don't know what the problem is and any help would be greatly appreciated.

Thanks!