We have been seeing multiple issues when restoring from azure devops private feeds.

These errors usually manifest in 401/403/404 errors when attempting to restore packages, and are caused by a mix of bugs in NuGet / The credential provider / MSBuild.

While we have some more information as to when the issues will be fixed, the azure artifacts team recommended a wokaround:

• Clear the nuget http-cache before attempting to restore any packages from these feeds
• Set the following environment variables:"
  NUGET_PLUGIN_HANDSHAKE_TIMEOUT_IN_SECONDS=20
  NUGET_PLUGIN_REQUEST_TIMEOUT_IN_SECONDS=20