After reinstalling, do I need to activate the scenery manually in the Scenery Library?
Surely not.
I have reinstalled, but keep getting the default scenery and FSDreamTeam is not showing up in the Scenery Library automatically.
This shouldn't simply happen. It won't hurt adding the scenery manually but, fact that hasn't appeared, is a sympthom something is wrong in your system.
Do you recall having seen any error message during the installation ? The installer checks your scenery.cfg file and, if something wrong is found, it will issue a warning and the installation will ABORT.
Which measn, if you have seen this message, adding the scenery manually to the Scenery Library wont' help, because the installation never copied any of its files, because of the error. The only fix in this case, is to fix your pre-existing error in the SCENERY.CFG, the installer should also give you a line number where the error was found.
IF you are sure you haven't seen any of this messages, and still the scenery is not added automatically to the Scenery Library, then it's something else which is very wrong on your system, probably related to wrong user permissions