Please install package: \'Xamarin.Android.Support.Design\' available in SDK installer. Android resource directory C:\\Users\\Srinivasarao\\AppData\\Local\\Xamarin\\Andro
Download android_m2repository_r25.zip related to API Level 21.0.3 and putit on this path C:\Users\USERNAME\AppData\Local\Xamarin Folders and Zip and extract it.
i hope it will work.