I just called TiVo and they walked me thru the steps to take to see if I am subscribed to Ch 506:
1. Tune to the channel in question;
2. Go to Messages & Settings > Account & System Information > CableCARD Decoder > CableCARD options (for installers) > CableCARD Menu > Conditional Access;
3. On the Conditional Access screen in the second "paragraph" find the line that reads "Auth:" "S" means Subscribed, "NS" is Not Subscribed
Apparently, I am somehow Not
Subscribed to FMC. I have a TiVo case # so now I get to call Comcast and plead my case once more (wish me luck).
TiVo (Comcast) Conditional Access Screen Shot