Star Trek: The Animated Series is something of a red-headed step-child for the vaunted sci-fi franchise. Conceived as a kid-friendly continuation of The Original Series' five-year mission, it was abandoned by Star Trek creator Gene Roddenberry and virtually ignored for many years. It has since been restored and is now widely available, but it's left a number of questions in its wake.
Source:https://www.cbr.com/star-trek-animated-series-canon/