All libraries on your account can be downloaded manually from the 'Instruments' tab of your account page.
Once here, navigate to the library you wish to download and click the icon in the bottom right corner of the instrument icon to bring up the manual download links.
We recently updated downloads to use zip files rather than many rar files, which makes extraction much easier. You can unzip the files directly from Finder/File Explorer by double-clicking on Mac, or right-clicking and selecting "Extract All" on Windows.
Alternatively, you can The Unarchiver on Mac, or 7zip on Windows to unzip the files.