I met this issue today and fix it by following: If you have delete the feed from VSTS, then you need to delete it from VS\Tools\Options\Nuget Package Manager\Package Sources: If you didn’t delete the feed in VSTS and want to use it, sign in with your VSTS team project account from VS upper right corner … Read more
It seems I fixed by adding to the feed’s permission settings the Build Service as Contributor. It’s a bit confusing tbh but it’s now working fine.
Download a copy of the installer exe from Microsoft: DotNetCore.1.0.0.RC2-VS2015Tools.Preview1.exe DotNetCore.1.0.0-VS2015Tools.Preview2.exe DotNetCore.1.0.0-VS2015Tools.Preview2.0.1.exe DotNetCore.1.0.1-VS2015Tools.Preview2.0.2.exe DotNetCore.1.0.1-VS2015Tools.Preview2.0.3.exe DotNetCore.1.0.1-VS2015Tools.Preview2.0.4.exe After choose this file when asked. Then you can successfully remove it.