I'm in the initial stages of setting a RX-V6A with an LG C1 and having sound issues.  I am using the eARC/ARC output from the receiver into HDMI 2 (which is marked eARC/ARC) on the TV using this cable from PBTech  and I am unable to get sound back from the TV to the receiver.  That is to say I have sound from the Sky Box, but if I use the YouTube app or play an MP4 via the TV USB input, I have no sound.

Is this likely to be the HDMI cable?  I have probably ballsed up the settings on the TV, but AFAICT I have it set to external speaker with the TV speaker disabled.

It's taken me three days to set up the speakers and lay the cables, but that includes putting a ceiling speaker hole in the wrong place.  I used that trick with the bent wire that you set to the radius of the speaker hole, and poke it through a small hole and if you can rotate it 360° you are good to go.  Unfortunately I found a joist/baton whatever 50mm clear of the drywall, which was not deep enough to clear the speaker, so I had to move the hole 90mm and patch the erroneous hole.  That was a mission all in itself as I am not the world's greatest plasterer, but I got it flat after realising I needed to thin down the last coat, but I have not exactly matched the texture of the rest of the ceiling. 

I started the installation after dropping my wife off at the airport for a two month trip to the UK to look after her mum, which is just as well as there is no way I could have made that mess while she was here!