Unable to play DTS-HD & True-HD

What do you hear? Do all other modes work ok?

If Audio Select (Page 44 and 98) is set to HDMI you will hear silence if no HDMI signal is present. I think AUTO is the best choice here.

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On Page 98 of the manual it says a bunch of things concerning automatic signal detection and input selection.

Initial configuration D) INIT. CONFIG
Use this feature to select the settings of the audio input jack select, active decoders and extended surround when you tum on this unit.
....

Audio select AUDIO SELECT
Use this feature to designate the default audio input jack select setting (see page 44) for the input sources connected to the DIGITAL INPUT jacks when you tum on the power of this unit.


HDMI set E)HDMI SET
Use this feature to select the component to play back HDMI audio signals.

Support audio S. Audio
Use this feature to select whether to play back HDMI audio signals on this unit or on another HDMI component connected to the HDMI OUT jack on the rear panel of this unit.
...

CHOICE = RX-V663

FUNCTION
Plays back HDMI audio signals on this unit. The HDMI audio signals input at the HDMI input jacks of this unit are not output to the HDMI component connected to the HDMI OUT jack on the rear panel of this unit.

CHOICE = OTHER
HDMI component connected to the HDMI OUT jack.

NOTES
This unit transmits audio and video signals input at the HDMI input jacks to the HDMI out jack only when this unit is turned on even if "S.AUDIO" is set to "OTHER".

I'd look in these areas for specific guidance.