favorites disappeared from cable box but are still available in the app

Same thing happened to me, re-adding the favorites doesn't update the guide. The fact that they persist on the app, but not the box seems like it might be a system thing.

Thank you for the additional information and for trying the troubleshooting steps we suggested! We'll need to take a deeper look into why your previously saved channels aren't being restored to your cable box. We appreciate you posting on our Xfinity Community Forum. I see you've also reached out via live chat, so we'll continue assisting you there.