Unable to add nuget packages - or open Workbook with nuget package

Running Xamarin Workbooks v1.3.1 and when I try to create a new workbook for Xamarin forms, the spinner keeps turning saying "Adding nuget package" when I try to add Xamarin Forms nuget package.

When I try one of the Xamarin forms workbooks examples from Xamarin GitHub, the workbook opens en Loading Packages keeps spinning on top without any result.

Tips on how to get this working?