Please share your template sensor config correctly formatted for the forum. https://community.home-assistant.io/t/how-to-help-us-help-you-or-how-to-ask-a-good-question/114371#oneone-format-it-properly-16
Where did you put the template: sensor?
It goes in configuration.yaml, not sensors.yaml.
If this is the first time you have created a template sensor you need to restart home assistant. After that you can use reload when adding new template sensors or editing existing ones.
Are there any errors in Settings → System → Logs relating to your sensors?