This happened a couple days ago and it came back up on its own. I am still on Shield 8.2.3.
Nothing has changed on my network. I can SCRCPY into my Shield without issue so it isnt network related.
The Channels DVR app is still there and enabled.
EDIT1: Log uploaded from Apple TV Client @ 9:27PM
Edit 2: Installed the Channels app on my shield and still no DVR service. I disable the service and the enabled it again and nothing.