Hello, new Character Creator user here (but not new to 3D).

I'm currently testing Character Creator to see if it's usable for a potential project.
I imported an FBX mesh head cloth. Followed the process of adding it with the automatic skinning in the default category.
It didn't fit perfectly, I'm trying to manually paint skin weights to improve it. However, the skin weights tool doesn't work. I don't see any red brush radius circle, no matter which bone I select.
My mouse cursor is a black arrow with a small black dot next to it.
See attached image. Am I doing something wrong? Is this a bug?

Okay, found the solution through exploration. Posting it here in case someone else will need it in the future...
It's not a bug, it's a feature.
The mesh was locked (little lock icon) in the scene window objects list. Would have been nice to get a warning pop up, since the tutorials don't mention this.