HBO announced early last month that it would retire its HBO Now (and HBO Go) app on second- and third-generation Apple TV set-top boxes at the end of April. Although that plan was extended for another two weeks, the video on-demand service's final moment on those legacy Apple TV models has finally come (via 9to5Mac).
As of this moment, the HBO Now app is no longer available on those older Apple TV units. If you use these set-top boxes to watch HBO shows through the Now app, you might want to switch to other hardware such as a newer Apple TV, a Roku, or Amazon Fire TV. Alternatively, you can subscribe to HBO Now through various providers such as Apple TV Channels. Amazon and Hulu also both offer HBO as a channel as well.
The move comes as no surprise since the third-generation Apple TV alone was released eight years ago. It's important to note that HBO Go is still available on those older Apple TV models, but not for long as the app will soon leave those devices, as previously announced by HBO. Also, you need to have an active cable subscription to use that streaming service.