Here are some things you can try to debug your error:
Analyse and tail -f the /crx-quickstart/logs/error.log file to see what the real problem is; there may be an exception. When the error.log is tailed, apply the same actions on how you would edit the policies to allow components to be authored on a given editable template.
Ensure that your basePage template is extending from the wcm.core.components.v2, to get the maximum benefit of AEM 6.5 and it's editable template features.
If you are completely stuck, start on a FRESH AEM author instance (with examples), and FRESH AEM project as an example. Build the a new AEM Project into your running local instance with the Adobe AEM Project Archetype. A fresh build will populate an editable template with examples of allowed components and policies for authors. Within AEM's crx/de, JCR, OR source code, you can analyse how editable templates are configured: https://github.com/adobe/aem-project-archetype