I have noticed that if I have no internet, when I try to open the Channels app, I get the “no tuners detected message”. I was without internet for approx 2 months, and today it was restablished and I was able to use again the channels app 
This sounds like an issue with your router. We regularly test our app with no internet and confirm it works as expected.
You could try entering the ip under Add Tuner Manually