NHL app

NHL is available as a separate app for the Apple TV set-top box. ‎NHL on the App Store. NHL is not in any way connected to or dependent on Apple TV+ or the Apple TV app. What is your model Apple TV? Identify your Apple TV model - Apple Support. NHL is available for Apple TV (3rd generation or later).

Apple TV+ is a subscription service for special original content within the Apple TV app. Both are independent of the Apple TV set-top box. The Apple TV app (or simply ‘TV’) is one of the icons on the home screen of the Apple TV box.

(Apple TV app icon on tvOS 13)

You can get the NHL app from the App Store on the device. If the app is/was already downloaded, then it may have been moved accidentally, and you will have to search more thoroughly.