That's the breaks. I continue to find myself adding optical cables when it fails. The good news is I don't do tech support for the companies so I only nod when folk want ARC to work.
I have a Panasonic TV TX-L42ET5B and Panasonic home cinema SC-BTT362 connected via the TV's HMRC2 ARC. I have an old non-HD PVR in AV1 and Wii in AV2. All work well together, the home cinema automatically switching onand off with the TV and all sound coming out of the home cinema's speakers. I wanted a HD PVR so have just bought a Panasonic DMR-HW220. I cannot get the sound to come out of the home cinema's speakers - if I plug the DMW-HW220 direct into the home cinema, or into the TV, as soon as I switch the DMR-HW220 on, the home cinema goes off. How do I set it up so that the sound does come out of the home cinema speakers? I bought Panasonic for compatability and to avoid these problems.