VM product detail page error

I have a functional web site in J2.5 VM 2.6 at http://palazzetti.ca using the gk_esport template>
I have created a new site and installed Storefront in J2.5 VM 2.6, as a first step to migrate in the future to J3 VM3.

I turned on VM Debug on the new site http://2015.palazzetti.ca
When I try to display a VM product page I get the following error:

Fatal error: Call to undefined method shopFunctionsF::renderVmSubLayout() in /var/www/vhosts/palazzetti.ca/2015.palazzetti.ca/templates/gk_storefront/html/com_virtuemart/productdetails/default.php on line 28

Suggestions?

There seems to be a conflict between the gk_esport and the storefront templates as they are both installed. In backend , if I switch back to gk_esport, the home page looks like gk_esport and the product detail works, but has the looks of storefront.
When I set the backend to storefront template, the detail product page produces the error.

To help you understand I created a superuser gavickpro for you to login.

I also tried to delete the esport template and the storefront template. Then reinstalled storefront. The VM product detail page does not appear.
I then installed SHOP AND BUY, and with this template the product page appears correctly. This tells me that the problem must be in the STOREFRONT template.