the audio for this disc is encoded in both standard dolby digital and DTS HD go into the disc's setup menu and select dolby digital and try it again. if it still is not working try selecting DTS HD MA, the receiver is able to decode both though, so maybe it's an issue of your BDP not bitstreaming it right.
I cannot recall a single DTS-MA bluray that even had a menu to select a different codec. Ok, I lie, Close Encounters of the Third Kind has a menu, but that's so we can select other lossless codecs.
DTS-MA is a dual bitstream; there is absolutely no need for DD. DTS-MA = DTS core + MA extension stream. Even with zero MA capability, there is nothing to select with an older legacy DTS receiver. It will still work fine.
dalessandro12, something is definitely fishy. I assume you have HDMI cable from receiver, directly to display. Nothing else really . . .
Does the 508 require input assignment? Is your HDMI Audio set to off? Believe it or not, this is usually set as off, and not on. On is for when TV does the audio by itself, and the speakers connected to the Onkyo are not being used. There may be an auto setting of some sort, but I am not familiar, because my projector does not have speakers.
I'm pretty confused, so I'm just trying to come up with something out of thin air.