Caller ID has disappeared....again

I have an older model  CONTOUR box (installed by COX about 2 years ago) and generally it works reasonably well.  However, the Called ID banner has disappeared from the TV screen once again.  It disappeared last about a month ago and I re-set the TV box and it worked again.  Today however I re-set the box and no Caller ID.  I checked and re checked the settings using the COX remote and it is all switched to on for Caller ID.  There seems to be no rational explanation for this behavior.  Can anybody assist?  Thanks!