Unable to authorize private NPM registry

I have a private NPM feed hosted on Visual Studio Team Service. I followed instruction on https://www.visualstudio.com/en-us/docs/package/npm/npmrc to setup the npmrc config.

After the setup, the registry URL and authorization token is stored in .npmrc file. I was able to run "npm install" command with success. However, I cannot list and install anything by using NTVS "Install new NPM package" window.

Expected Behavior

All packages in the registry will be listed

Actual Behavior

No package is listed.
An error shown "Refresh failed - see output below for details"

Full Stack Trace Below

System.Net.WebException: Remote server return error: (401) Unauthorized
   On System.Net.HttpWebRequest.EndGetResponse(IAsyncResult asyncResult)
   On System.Threading.Tasks.TaskFactory`1.FromAsyncCoreLogic(IAsyncResult iar, Func`2 endFunction, Action`1 endAction, Task`1 promise, Boolean requiresSynchronization)
--- End of stack trace from previous location where exception was thrown ---
   On System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   On System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   On Microsoft.NodejsTools.Npm.SPI.NpmGetCatalogCommand.<DownloadPackageJsonCache>d__21.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   On System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   On System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   On Microsoft.NodejsTools.Npm.SPI.NpmGetCatalogCommand.<UpdatePackageCache>d__27.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   On System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   On System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   On System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd(Task task)
   On Microsoft.NodejsTools.Npm.SPI.NpmGetCatalogCommand.<ExecuteAsync>d__23.MoveNext()

Environment

• NTVS Version: 1.3.41102.00
• Visual Studio Version: 15.0.0-RC4
• Node.js Version: 7.6.0
• NPM Version: 4.2.0

Steps to Reproduce

1. Setup .npmrc with a private registry that require auth
2. Open "Install new NPM Packages..." window

Reproduce the failure with a private authenticated registry using the .npmrc setup and the “Install new NPM Packages...” window. Start at Microsoft.NodejsTools.Npm.SPI.NpmGetCatalogCommand, especially DownloadPackageJsonCache and UpdatePackageCache, and trace how the registry request is authorized. Done means the window lists packages from the private registry without the 401 error.