Whats does this mean? Do I have a reception, network or a HDhomerun problem?
Need more details. What device are you on? At home or remote
2 ATV and 2 4Ks - at home hard wired
Next time this happens go to the bottom of the Settings tab and click Submit Diagnostics > Video Player.
Usually Tuner Not Available means all your HDHR tuners are in-use. But it can also mean other things- maybe the IP of your HDHR changed, or something else.