Fixed audio

I realize my problem may have nothing to do with the receiver ( TX-DS555) It has always worked well till I hooked a sharp LC-70LE732U to it. The Digital auto out to the receiver is fixed. I believe I know the setup on both units and have the correct type of cables. At this point I have only the HDMI from the STB to the TV and the digital out from the TV to the receiver. I can not increase the volume out of the TV or the reciever does not process the increase. The TV screen shows the level is increasing. Changing from fixed to variable out only shuts off TV speakers. I still get a fixed level. I can increase the receiver volume and its ok. My wife has trouble with 2 remotes or changing the inputs. I have talked to the costco people and they called sharp. Sharp says it must be the receiver is not set up for that type of digital? It passes digital auto and works fine using the reciever controls. It sends the same level out in either mode 1. fixed 2. variable. Would a bad cable pass a fixed level only? Sharp also said the reciever does not handle dolby digital it's will need to be set to PCM. Lost me here.
The receiver has always handled Dolby. A very slight touch on the Cable remote control jumps the reciever volume too much. very hard to find the right level. The last TV was easy to adjust. Please reply if you can add anything or need more info. Thanks Lyle

Hi Lyle,
I am looking into it and will get back to you soon, thank you.