Resolved
The issue has been fixed: https://github.com/NuGet/NuGetGallery/issues/3961#issuecomment-301917548
May 16, 2017, 23:43 UTC
Identified
The root cause of this issue is NuGet's CDN. We are currently working with NuGet team to resolve the issue (https://github.com/NuGet/NuGetGallery/issues/3961) and NuGet team is working with their CDN provider. Sorry for the inconveniences.
May 16, 2017, 18:44 UTC
Investigating
Some preliminary investigation makes us believe that the root cause is NuGet's CDN in US region as explicit resolving of <code>api.nuget.org</code> to a different CDN region (EU or TW for example) fixes the issue.
May 16, 2017, 00:14 UTC
Investigating
Starting on Thursday, May 11 we started seeing intermittent issues with downloading NuGet packages on our primary environment.
While we are investigating the root cause make sure your builds are using nuget 3.5.0 which is installed by default on build worker VMs and available in PATH. NuGet 3.5.0 has better support for timeouts/retries management. Also, to retry nuget restore use `appveyor-retry` script like that:
<pre> appveyor-retry nuget restore <path-to-solution></pre>
May 15, 2017, 17:55 UTC