Whole home dvr

Recently upgraded to whole home dvr, Technicians installed one host box in the living room and two regular boxes in two other bedrooms. Everything works fine except one of the bedroom boxes the dvr does not work. Every other function of the box works until you press the dvr button its says service is unavailable. Called about the problem, a tech has been out twice, changed the box and still cannot correct the problem. Any help would be appreciated as i feel i have been left out to dry by cox.