You need to select another black and white profile than camera monochrome. Camera monochrome is a profile that mimics the in-camera jpeg rendering when you set the camera to do a black and white and cannot be tweaked. All the other black and white profiles such as Adobe monochrome can be tweaked.
Thanks. I just updated and clicked Treatment: Black & White. I didn't know that I also had to go to the Profile button underneath to pick the Adobe Monochrome profile.
Normally it should default to adobe monochrome for new images. In this
case, it probably took the last black and white profile you used on that
image. Something to watch out for.