Things to check if you experience missing tv channels in EPG:-
A] Go to Zap2it.com and check the channels listed there or not.
B] If the channels are listed in the website but not in your EPG then try the following:-
Open Windows Media Center Tasks > Settings > TV > Guide > Edit Channels.
Check whether the channels listed are marked;if not marked they will not appear.
C] Sometimes using a Zip Code,which is near by to your location helps.
D] You may post the issue at Microsoft Connect
For this you need to sign in or sign up and click Submit Feedback button to raise the issue.Don’t forget to P provide more information about your guide listings. At the Windows Media Center Start menu, go to: Tasks > Settings > TV > Guide > About Guide Listings.
E] You may try Guide Tool also for adding missing channel
F]If you have a a QAM capable PC tuner you may need view the following Youtube video to get a clear idea:-
6] If you need to remap then remap the clearQAM channels.
7]If Automatic Download Guide listings doesn’t help then opt for add channels manually.Make sure no firewall or internet security app is trying to block.
7]Don’t forget to update your tv tuner card or graphic card before proceeding.Just visit the websites of the manufacturers to grab the latest drivers.