.NET Core
In .NET Core, NuGet packages are now stored in a global location, by default:
Windows: %userprofile%\.nuget\packages
(aka C:\Users\[User]\.nuget\packages)
Linux: ~/.nuget/packages
Additionally, the packages.config was removed with references now being stored using the <PackageReference> element in the .csproj file.
You can find out more documentation here.
If you can’t find the global location, it may have been changed. You can discover it using this command:
dotnet nuget locals global-packages --list
If you would like to change the package location to, for example, e:\packages, you can use the following command.
dotnet nuget config -Set globalPackagesFolder=e:\packages
Any problems installing NuGet packages that I’ve had have always been fixed by clearing all the cache locations (there are additional places where NuGet packages are saved aside from the global location) like so:
dotnet nuget locals all --clear