I, too, am having difficulty getting the HDMI-ARC to work properly. Everything was working fine, till I recently upgraded my cable box to a Samsung Enhanced DVR.
So previously, when I turned on the components, Cable TV was default and the audio played through the speakers. When I turn on a smart app or USB drive, the receiver switches to ‘TV AUDIO’ and the sound played through the external speakers.
Now, after the new cable box has been installed, the only way I can get Audio from a smart app or USB drive to play through the speakers is to turn everything off, unplug the HDMI from the cable box, turn on everything and then plug the cable back. Then the Audio will play fine from the TV through the speakers and I can control the Pi with the TV remote (Anynet connects). But once I turn off everything and back on, the Audio does not play. Everything else like Video and Volume Control of the receiver works fine except Audio Out through speakers.
I understand that the other solutions are to have Optical Out or to use CC330i’s / mike81’s connection suggestions. But I would prefer this HDMI ARC use as its easier and it worked fine before.
My setup - Cable Box, Raspberry Pi and PS4 >> Receiver >> UN55H7150