Assuming you’ve downloaded the zip version from here.
Everything from the ext_libs directory (within the zip file) needs to be copied to
either the notepad++ installation directory OR if you used the %APPDATA% configuration then it needs to be placed to the %APPDATA%\Notepad++ directory.
The same applies to the xmltools directory, which only has one file XMLTools.dll.
If you used %APPDATA% configuration, than copy it to %APPDATA%\Notepad++\plugins, if not using it, than copy it to the plugins directory under notepad++ installation directory.
If it still doesn’t work, may I ask you to post the debug->info (avaliable under ? menu)
Cheers
Claudia