The volume control for spotify connect devices does not function in the touch bar anymore (volume controll for spotify connect directly in the spotify app still works). I already talked about this with the macbook support. It seams like it is a problem with spotify that needs to be solved via Update of Spotify. I am using MacOS 10.14.6 with Spotify 126.96.36.1992.g55a4b852.
Already tried adding a new user in macOS and also clean installed Spotify again (and also tried the feature with different spotify connect devices).