remote control will not control volume - DirecTV

Recently purchased a Sceptre 55" 4K HD television. Trying to program the remote to the Sceptre tv. One function will not work...can not get the volume control to work, neither up or down will work......the mute feature does work. Power on and off works as well. Again, sound MUTE does work but volume UP and volume DOWN does not work with the Direct remote control. The Direct remote is model RC66RX. The receiver is Model: HR44-200
The remote functioned properly with all functions on our old Vizio problem at all.

any help or suggestions are much appreciated

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