There could be multiple reasons but few things worth checking first before starting a ticket:
1) Make sure your Bluray player is setup for 1080p output. Anything else will create issues with mulitchannel due to bandwidth requirements of 8ch out @ 96kHz enabled at all times on the nanoAVR.
2) If you are running an older firmware, make sure that you've upgraded to the latest version (v1.12 and up). You can find the latest firmware version from the UserDownloads section of our website.