Unity Packages fail to load

Long file paths

at System.IO.__Error.WinIOError (System.Int32 errorCode, System.String maybeFullPath) [0x000c4] in <eae584ce26bc40229c1b1aa476bfa589>:0 
at System.IO.FileInfo.get_Length () [0x0003f] in <eae584ce26bc40229c1b1aa476bfa589>:0

If your plugin package is saved in a folder with a long file path, you may encounter errors like the one listed above when loading some of the packages. To fix this, move the packages to a folder on your computer with a short directory path - e.g. C:\unityplugins\ - and install them from there.