I checked in a project on one computer, checked out on another, and find that the binaries installed by NuGet are missing. I could check them in to source control as well,
If the error you are facing is "unable to connect to remote server" as was mine, then it would benefit you to have this check as well in addition to the checks provided in the above comments.
I saw that there were 2 NUGET Package Sources from which the packages could be downloaded (within Tools->Nuget Package Manager->Packager Manager Settings). One of the Package Source's was not functioning and Nuget was trying to download from that source only.
Things fell into place once I changed the package source to download from: https://www.nuget.org/api/v2/ EXPLICTLY in the settings