Sony HX750 with Sony BDV 990W home theater

Hi, I have a Sony HX750 46" Bravia 3D LED TV and Sony BDV N990W Home theater system. Everything works from Home theater end- the USB, DVD and outputs to TV correctly. I have a DTH at home with HD connecting via a HDMI cable to TV using HDMI 4 channel and Home theater connecting to ARC HDMI 1. My problem is that TV sound doesn't come out on the Home Theater, the service engineers brought a HDMI 1.4 cable and tried and nothing comes out of TV but the analog 1:2 cable works but sound out is not good and very low even at max volume. What could be the problem? when we do a HDMI Sync from TV remote the HDMI Sync menu is greyed out and basically the Sony servicing have tried with many HDMI cables but doesn't work and both TV and Home Theater is less than a month old and very depressing for me as it is not serving the purpose. Can you please help