IR echo not working for cable box

I have setup my slinke to take IR from all my rooms and echo onto one IR emitter. This emitter then flashes onto my devices. This works fine for all dveices except my At & T digital cable box. ( the manufacturer is General Instruments).

What would be the problem? Has anyone encountered this before? My scenario expects that I should be able to echo all device commands from any room for any device. Thx in advance.