Whenever you insert Pretest slides, the skin editor will be disabled automatically for the whole file. And no way to turn it on. If you want a playbar, you'll have to use normal question slides for Pretest (with its consequences) or use custom question slides for pretest.
Branch aware has nothing to do with that, really puzzled by that first answer. And the only other possibility is that you decided to turn the skin editor off yourself. For normal question slides you can turn the playbar off but you decide as well.
Lilybiri