Hi CISParts,
I don't think your error is caused by the changes you have described. As if you use the ShopAll theme then the ProductTemplate.xxx files are loaded from the Themes\ShopAll folder and not directly from the Views folder as you have shown. You should have done something else that causes this error.
P.S: Isn't the error because you are trying to open the product template file in the browser? VS usually tries to open the same Razor view file you are editing when you start debugging but these files could not be accessed via web they are used by the MVC framework only.
Hope this helps!
Best Regards,
Nop-Templates.com Support Team