Working within quite a restrictive company proxy, I updated visual studio 2017. Since that time, when I run Android SDK Manager, it cannot access the Microsoft Repository, though the Google repository works. When I try Android Device Manager, an error pops up with "Android SDK instance could not be loaded. Please check your internet connection."
It seems very likely to me that some attempt to connect outwards is being blocked by my proxy, but I cannot find out what url this is. Does anyone know?