Xamarin.Forms.GoogleMaps.iOS.PlatformConfig issues

[karitall56]

Suddenly I get problem when building my Solution.
Error Text:

Can't resolve the reference 'System.Boolean Google.Maps.MapServices::ProvideAPIKey(System.String)', referenced from the method 'System.Void Xamarin.FormsGoogleMaps::Init(System.String,Xamarin.Forms.GoogleMaps.iOS.PlatformConfig)' in 'Google.Maps, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'

Looking to prior conversation I have tried to downgrade Xamarin.Build.Download (currently 0.11.3)
Using Xamarin.Google.iOS.Maps 6.0.1.1
Have deleted .bin .obj files and Rebuild solution many times.

Any clues what to do?