An error occurred while trying to restore packages. Please try again

This is how I fix my issue:

First, I clear my Package Cache:

Second, I make sure I have the right path source and click the available package source:

1. Make sure you upgrade to the latest NuGet (http://docs.nuget.org/docs/start-here/installing-nuget).
2. Make sure you're doing package restore "The Right Way" http://blog.davidebbo.com/2014/01/the-right-way-to-restore-nuget-packages.html

That should resolve the issue.