Could you please clarify is this an upgrade project or not? In general it is important to be clarified which is the previous version of the product (the version that you upgraded to latest Sitefinity version 6.3)?
Could you please verify if the Ecommerce module is activated (Administration -> Modules & Services)? If the module is not activated (e.g. failed or inactive) could you please try to activate the module (for Ecommerce module in Actions menu -> Activate)?