Is this issue with all channels or only few ones ???
These are the following reasons for that error:
1. Your subscription has ended and u need to re select your package and call LCO.
2. Hathway has blocked the channels for you, need to see other users in your area
3. Some technical error which happens, need to call hathway
Lastly your STB-Smartcard pairing has been undone, this is unlikely