How to enable Product image zoom hover function

Hello,

I am trying to get my image product images to have the demo zoom hover function but is not working on my product pages but is working on non product pages. I was wondering how to get this hover zoom effect to work.

P.S. an employee who use to run the website posted a topic of mine about how to disable this function using code in the function.php. I have looked through the current function.php and cannot find this code they posted and am not even sure if its in the .php file to cause the image hover function to not work any suggestion or is there a way to reset the function.php to its default code.