I've used Channels on 2 different Apple V's for years without issues.
Now suddenly I have now signal from the HDHomeRun tuner.
The signal is good into and out of my router. I can access Channels just fine from my phone or computer. I haven't made any changes to the system. Tried restarting Apple TV and uninstalling and reinstalling the Channels app.
Not sure what to do to fix things.
Can you click Submit Diagnostics from the app?
What exactly is shown when you try to play a channel?