Xamarin forms FileNotFoundException Xamarin.Android.Support.v4 ( Visual Studio)

I Have been trying to use maps in Xamarin Forms in Visual Studio, but when I finished this error show up:

Severity Code Description Project File Line
Error Exception while loading assemblies: System.IO.FileNotFoundException: Could not load assembly 'Xamarin.Android.Support.v4, Version=1.0.0.0, Culture=neutral, PublicKeyToken='. Perhaps it doesn't exist in the Mono for Android profile?
Nome do arquivo: 'Xamarin.Android.Support.v4.dll'
em Xamarin.Android.Tuner.DirectoryAssemblyResolver.Resolve(AssemblyNameReference reference, ReaderParameters parameters)
em Xamarin.Android.Tasks.ResolveAssemblies.AddAssemblyReferences(ICollection`1 assemblies, AssemblyDefinition assembly, Boolean topLevel)
em Xamarin.Android.Tasks.ResolveAssemblies.Execute() Driver.Droid

I didn't know what is it. I saw that have the same problem in Xamarin Studio, but I really noob to know how to fixed it in Visual Studio. By the way Now when I start a new project this error show up.
What should I do?