This happens if you mistakenly removed some files manually (maybe long ago), so the uninstaller doesn't display.
In this case, manually remove it from the Scenery Library FIRST, THEN remove the following folders:
- fsdreamteam\OhareX folder
- Simobjects\Misc\FSDT_OhareX folder
both under the main FSX folder, then install the 2.0 version.