For me that just an emulator issue. MoveToRegion & Geocoder seems to not work in emulators, so I found a Android Device ( Android 5 ) to test and it works.
For map, you should use true device for testing.
Ok I found a solution for the MoveToRegion
When I use GetPositionsForAddressAsync it thrown this error :
[MonoDroid] UNHANDLED EXCEPTION: [MonoDroid] Java.IO.IOException: grpc failed [MonoDroid] at System.Runtime.ExceptionServices.Exception…