Iam having the same issues with the LG C9 when using Dolby Vision on HBO Max through a Chromecast. I also have a Bose soundbar. I decided to try and watch Dolby Vision without the soundbar as the sound option and it worked flawlessly.
As a workaround, I then changed the audio back to the soundbar and I'm still having no issues. Annoying but at least a temporary workaround
C9 Update - 05.10.04 - Can no longer connect to Dolby
in LG TV and LG webOS Smart TV Discussion
Posted
Iam having the same issues with the LG C9 when using Dolby Vision on HBO Max through a Chromecast. I also have a Bose soundbar. I decided to try and watch Dolby Vision without the soundbar as the sound option and it worked flawlessly.
As a workaround, I then changed the audio back to the soundbar and I'm still having no issues. Annoying but at least a temporary workaround