Saving a CPTL as a CPTX in Captivate 9?

A cptl file is a template, it is meant to be used with the command 'File, New project from Template'. In that case you'll get automatically a cptx file. You can save a cptx file as a template, to be used that way, but not the other way round.  Look at this article to see differences between the much more flexible themes and templates (which have also some issues):

http://blog.lilybiri.com/whats-in-a-theme-a-template