I don’t use dark sky and I also did not write the template that you’re trying to use. A good place to start to troubleshoot would be to go to “developer tools” in your sidebar, then “templates” and test that the templates you’re using are reporting data. Example to paste into the template editor:
{{ states('weather.dark_sky') }}
{{ states.weather.dark_sky.attributes.temperature }}
Discussions on this unsupported CH “feature” should be posted here.