Basically MPro (by default) will only "tree-view" the subfolders once it deems it is worthwhile to do so ie. you have two or more subfolders within any given folder. This can be a little disconcerting if you aren't expecting it. The reason is simple - if you have a tree of single folders, then there's little point displaying it as a "tree" cos it means lots of extra clicks. (At least, I think that's the logic). Mpro tries to intelligently "collapse" the tree so that you don't have unnecessary entries.
So, as demo - make a folder called Family
Then one called Family.Brother