If you go to the Conditional Access menu then look at the 'CON' setting it should say Yes. That is what happened to me on every card that was bad. If you plug in your cablecard and you get OOB frequency and an OOB Lock and your signal strength and quality are at 100% but you get no Card Validation or Channel List. If you have X1 equipment with a 'point of entry' filter on your house then the box will not be able to validate. I'm sure Comcast has to support cablecards by law or something, because they sure don't like supporting them. I would think Comcast should be checking their cards, but they have no cablecard devices to check them in. Good thing too because they had no more in stock they were going to have to order one.Thank goodness that one worked. So I exchanged that one and the 7th worked. But the two new cards and the 2 hdhomeruns would not work.

After 2 bad cards I bought a second hdhomerun just to be sure.

The Cablecards came from a Comcast office. The first 4 cable cards I got did not work and it was not the hdhomerun. I'm not sure about other providers but Comcast seems bad about cablecard support.

Plex cablecard tuner