I have the exact same problem as orginal poster.
GX 2007, and I belive that the amp is the same model. My service told me that I may require replace the amplifier.
However, a couple of days after the audio came back. it was working fine for a couple of days.
Now sound is being dead again.
I asked for estimate again, see how much they are going to charge me.
and I will try to negtiate with them since the latest ml amplifier seems to have troublesome.
I will update the status as it progress.