Could not restore packages

Hello, I am trying to run a blank app in visual studio community for mac and I am getting this error.

Field 'System.Net.ExceptionHelper.WebPermissionUnrestricted' not found.
Failed to retrieve information about 'Xamarin.Forms' from remote source 'https://www.nuget.org/api/v2/FindPackagesById()?id='Xamarin.Forms'&semVerLevel=2.0.0'.

When I check in preferences-> nuget -> sources I get this message:

Any help on how to fix this issue?
Regards, Bruno.