Every template corresponds to a specific web engine. To use that template, you must have that web engine installed. For example, you cannot load a template for TTG CE3 Gallery if you do not have TTG CE3 Gallery installed.
Our templates are named to indicate to which engine they correspond. For example, the template “CE3 Asphalt - Gallery” belongs to the Asphalt theme and corresponds to TTG CE3 Gallery. The “CE3 Asphalt - Pages” template also belongs to the Asphalt theme, but corresponds to TTG CE3 Pages.
To transfer settings from one template to another for use with a different web engine, see our tutorial Share Templates Between Engines. Though I will endeavor to cover all of our CE3 engines within each theme pack.