Comcast may have your channel lineup online at https://www.xfinity.com/learn/channel-lineup or https://www.xfinity.com/support/local-channel-lineup/, or they may have included it with one of your recent bills. Check https://customer.xfinity.com/.
Service Centers and Xfinity Stores should have printed channel lineups. Check locations and hours at http://www.xfinity.com/support/service-center-locations/ to pick one up, or call Customer Service at 1-800-Comcast and have them send a lineup to you.
what station is TBN on
@ebacal , what is your ZIP Code? TBN appears to be a network carried by local stations (the way, say, ABC, CBS, and NBC are). It is possible that your local area's TBN station decided to switch to another affiliation.
According to the TBN station list, there are four cities that should be broadcasting it on "channel 21":
WMPV, Mobile, AL
WTCE, Fort Pierce, FL
WTPC, Virginia Beach
Are any of these in your area?
For those who have the national feed of TBN, you should be able to find it on channel 1661. Lower channel numbers vary from area to area.
For those of you who have a localized feed, these channel numbers vary from area to area.