I have had a similar problem several times. This morning I took the attached picture. The sound settings were unavailable for about 5 minutes while I was driving. Then, without any actions on my part, they became available. I noticed that my ANDROID AUTO connection, which established wirelessly when I got in the car, reset at the same time the sound settings returned. Something must have happened with the software resetting or partially resetting.Solved! I turned on the radio, and then, even with the radio off, the sound settings came back. Obviously a bug. (A reboot of the infotainment system did not help)