I was fighting with my new bravia for ages until I realized there is a mute slider on the back of the TV. OOF.
If you are not going to log dive with ADB then your option is to pray and then revert to a factory image. If your microphone is in the remote then have you considered the remote is dirty, low batteries and/or dead?
I have a similar issue, it stopped working like a month ago, I have not fixed it yet.