Hi
Thanks for sharing further information and even the pictures...not sure which brand the HDMI cables are, if they are of high speed and Bandwidth then it should work. Also the HDMI version is important.
While I understand most of us are very anxious to get things up and running immediately, connections and settings need to be paid attention to and done appropriately to avoid such challenges etc.
Is the HDMI Control settings set to ON for both the AVR and the TV? If not done then the ARC function does not work properly.
See the links below.
Ideally, I would connect the STB in a separate HDMI input on the AVR then connect the TV output to a Coaxial or Optical input of the AVR...like this it The TV and STB would be on different sources on the AVR.
I would only use the HDMI out of the AVR to connect to the HDMI input of the TV to display video information of sources connected through HDMI on the AVR......i.e STB only.......Blu Ray Player......it will also send audio to the TV so that it can be heard through TV speakers....most of us have connections this way done and it works well.
Anyways you check and try the HDMI control settings on both if it is ON and see if the issue is resolved. If not the the only way I see is the suggested connection way which most of us have done.
Also note that most of us are either busy with work or other stuff and when time permits, someone would try to review and respond where possible to any challenges or queries. You will need to wait for specific answers or responses or advises. Most of us are quite passionate about AV products etc. and thats why we try our best to dedicate some time and help each other in order to improve the AV experience and knowledge share.
Hope the issue gets resolved.