A family of Microsoft word processing software products for creating web, email, and print documents.
Double-clicking a template (*.dotx) file should still create an unnamed document based on the template. Try repairing your Office installation. Choose the online repair option, if it is available. Note that an online repair usually requires that you re-active Office, for example by signing in to your Office account (or by entering a product key). See https://support.office.com/en-us/article/Repair-an-Office-application-7821d4b6-7c1d-4205-aa0e-a6b40c5bb88b.