For about 3 days on my FireTV nothing live has played. DVR has same issue, but getting about 100mbps down when I check the speed. Tuner is found but just get a black screen instead of channel video. After about 5 minutes of searching it says no tuner detected and then finds a tuner and goes back to the guide.
Still works on my Shield and my Pixel3XL. Have deleted and uninstalled both the HD app and Channels app. Also I should mention channels do play on native HDHR app.