In Smith Cart v3.85 release the product details page has been split out as a separate module so you will need to create a new page and add the product detail module to it. Please take a look at the quickstart guide for more info http://www.smith-consulting.com/Portals/0/docs/smithcart-quickstart.pdf
Try going into the module settings and re-saving the settings. Do this for all the modules you are using buynow, minicart, featured products etc.
-Scott