I started blank cross-platform projects in Visual Studio 2015 update 2: Visual C# -> Cross-platform -> Blank App (Xamarin.Forms portable).
It created 6 projects in t
Xamarin Forms is not always compatible with the latest version of the Google Support libraries. Xamarin publishes them so Android developers (not using Forms) can utilize them if they need them, but Forms developers can continue to use the older, compatible versions.
When I was trying to update the NuGet Packages for one of my Xamarin project, I got the error same as this..
Please check Compile framework and target framework of your android app.. and update your NuGet packages according to the properties of your android app. Below link describes how did I fix the issue.
https://xamarinsharp.com/2017/05/01/xamarin-android-support-design-25-3-1-is-not-compatible-with-xamarin-forms-2-3-4-231-constraint-xamarin-android-support-design-23-3-0-how-to-fix-it/