Microsoft's Band 2 wearable is no longer supported by Cortana on Android
You won't be able to locate this change in the latest "what's new" patch notes in Cortana's Google Play Store listing, but after pressing "Read more", one can see the update being mentioned in the last sentence of the description:
Albeit being chock-full of features and receiving mostly good reviews, the Band 2 didn't exactly achieve a slam dunk. An initial asking price of $249.99 (some smartwatches sell at half the price) and a below-par battery life effectively prevented the fitness tracker from being a success. The gadget was pulled from the Microsoft Store and several brick-and-mortar retailers back in October, and the manufacturer hasn't revealed much regarding the future of the Band ever since.