WiFiManager.ScanResults now work. error

I have two projects. The code for both projects is the same and the permission settings in AndroidManifest.xml are the same.
But one project works well. However, one project works fine and the other project always returns an empty list.

var wifiManager = (WifiManager)Android.App.Application.Context.GetSystemService(Context.WifiService);
IList<ScanResult> list = wifiManager.ScanResults;