So we both are doing the same thing.
Start on Xfinity Home Page. Click on TV at the top of the page. On the next page Click on WATCH ON TV near the top of the page.
You should now see TV listings which looks like a channel guide. Look at the top left of the Listings box - do you see your ZIP CODE? If no input your zip code. If yes lets change it to another zip (use mine in EST 15066) then change it back to your zip code. NOTICE IF THE TIME A SHOW IS ON - IN THE LISTINGS - CHANGES WITH THE ZIP CHANGE.