Apple tv

on a tv one use the remote of the tv to choose what input source one wish to input from so say the appletv is connected to hdmi1 and an xbox is connected to hdmi2 then you choose the one you wish to get input from on the remote

for most tv clicking on the channel + / - buttons will make it stop using the hdmi port as active input and rely on the build in tuner, if your other channels comes from some setup box for cable you need to choose that hdmi port as active input source. all this is 100% your tv's functionality

Again, you would be switching to another input to use Apple TV so of course it’s not going to show your tv channels. If you switch back and it’s not working then it’s an issue with the antenna, Apple TV has no bearing on that.

If your Apple tv light is flashing then that has nothing to do with your TV channels, your Apple tv needs to be restored

https://support.apple.com/en-ca/HT203028

Apple TV is a media streaming device, it is connected to another input. You would need to switch inputs to go back to your Tv channels.

Then that indicates a hardware issue. That model is discontinued but you could try taking it to Apple