For more than one project SourceTree does not list untracked files in the Unstaged files list. I can use the terminal and git status to see the untracked file. I confirmed that nothing in the .gitignore would ignore the files. The projects' full path has a space in it, but their relative paths do not.

If I use git add in the terminal to add the untracked files, they then appear in the staged area of SourceTree. If in SourceTree I uncheck the staged, new file, the file is not moved to untracked under unstaged files. This occurs for files in the root of the project and in subfolders that have other tracked files.