Since ever, it is not possible to create site templates from sites with activated publishing feature.
In SharePoint 2010, it was possible to deactivate the publishing feature and then create the site template. But in SharePoint 2013, also after deactivating the publishing feature, it is still not possible to create a site template.
But there is an option to get the it working again.
You have to do the following:
- Open the site in SharePoint Designer 2013
- Click “Site options” in the ribbon
- Set the parameter “SaveSiteAsTemplateEnabled” to “true”
That’s it. Now you can save your site as template again!