Is possible that after you donwloaded the BIG file, your Launcher could not install it because the original file is occupied.
Then you have to close the Launcher and copy it by hand renaming in RFV3UP.dck
(pay attention to make a copy of the original file)
The destination directory is: c:\Program Files\RealFlightG3\Data
Then you have to close the Launcher and copy it by hand renaming in RFV3UP.dck
(pay attention to make a copy of the original file)
The destination directory is: c:\Program Files\RealFlightG3\Data