Why are my Touch Bar volume controls grayed out (disabled)? I’m unable to adjust the volume using my Touch Bar, how do I get out of this mode?



(as you can see the volume buttons are disabled).
I experienced the same problem. The fix:


Open System Preferences > Sound
Select the Output tab
Select MacBook Pro Speakers (or another working output) under Select a device for sound output.


The cause: I connected my MBP to an external monitor, which, unbeknownst to me, had speakers of its own.