Adding Android to existing PCL/iOS VS project

I just purchased a Xamarin.Android license, downloaded and installed the SDKs and then added the Android blank project to the solution. When I tried to add the Xamarin.Forms nuget package to the project, I get this error:

Attempting to resolve dependency 'Xamarin.Android.Support.v4 (≥ 21.0.3.0)'.
Installing 'Xamarin.Android.Support.v4 21.0.3.0'.
Successfully installed 'Xamarin.Android.Support.v4 21.0.3.0'.
'Xamarin.Forms 1.4.4.6392' already installed.
Adding 'Xamarin.Android.Support.v4 21.0.3.0' to CloudCopMobile.Android.
Uninstalling 'Xamarin.Android.Support.v4 21.0.3.0'.
Successfully uninstalled 'Xamarin.Android.Support.v4 21.0.3.0'.
Install failed. Rolling back...
Cannot get libraries from incompatible component