I am getting: "Fatal error: Call to undefined function mp_products_filter() in /home/

I installed Gridmarket and tried looking through the product that is listed on the site and I get this code: "Fatal error: Call to undefined function mp_products_filter() in /home/content/18/10790718/html/wp-content/themes/gridmarket/mp_category.php on line 8".

I have read somewhere that Marketpress plugin needs to be activated, which it is. I can't seem to figure out why I'm getting this error.