I upgraded to the latest version of the iPad Xfinity app a few months ago and now can't use it to record a program in advance. My DVR is not listed as a device in the app and when I go to Xfinity.com and list my devices, the DVR is shown as "failed". The DVR works fine locally. The old version of the Xfinity iPad app worked.
Have you tried signing out then logging back in? I was having the same problem (although my DVR wasn't showing as Failed) and the remote app found my DVR again.