Hi, please help.

I recently purchased a BDP5100/12 as secondary unit for my kitchen which was used on a (old) plasma TV, I upgraded the 5100 to 1.62 firmware and have used it to watch many Blu-Rays, DVD's, Video and Music over my LAN without any issues. I thought I would give it a go on my main setup and this is when I tried the audio into a AV AMP and found no audio was being detected out of the digital coax port on my AV AMP.

I've tried several DVD's and several Blu-rays, I've change each of the audio options on the 5100 in turn to each setting and my A/V AMP (Pioneer VSX-515) doesn't detect any audio input. The AV amp works fine, I'm sure since I've used it with various other DVD players and media players (before and after using the 5100) using the digital audio input. Normally it detects automatically analogue or digital / dts / dolby d / etc. and I can manually change it.

Any ideas why I am not getting audio output? I don't have a HDMI TV as I use slightly older professional plasma monitors with VGA/RGB input, I was doing to test the 5100 on my parents TV to check at least the audio worked through HDMI but I really want digital out on the coax port to work. The RCA Stereo out works fine. The digital coax port feels solid and not broken.