Skills, like most apps, can have problems and glitches. If for some reason a skill isn't acting properly, it's best to disable and enable it again first. This usually fixes most problems. Of course, you could also check other skills. Assuming all of your skills are having issues, you may want to check your internet connection. If the skill is brand new, then there's likely an issue with the Settings. Some skills require parental controls while others may need you to tap 'Enable' again. If it's an issue with a subscription, make sure that you're signed into your account.