I was trying to change site template with site that I had saved. The target site was using project site template and the solution was activated. Checking on Microsoft site, I don't understand what this if it appropriate means. Is there something that I need to do before I could setup this project site template.
I knew I have to do something to make it enable. In Site Creation option you need to choose either Automatically create a site on next publish or Allow users to choose.
it then became enable.