Visual Studio activation error

I am not able to connect to Xamarin from Visual Studio. What should I do?

My company purchased several Xamarin licenses for the team, but I get an error when I try to login with Visual Studio.

1. I open the XamarinStore.sln with Visual Studio 2013 or Visual Studio 2012 (tried both)
2. "Using Xamarin.iOS with Visual Studio requires Business edition or higher. Please log in with your Xamarin account to proceed."
3. I enter in my email address and password then click "Log In"
4. I then get a Windows authorization dialog (like the one you get from Internet Explorer) titled "Connect to auth.xamarin.com" with the
text "Connecting to auth.xamarin.com" asking me for User name and Password.
5. I try to enter the same credentials from step 3 into this dialog box and click OK.
6. Goto step 4. This repeats infinitely until I click cancel.
7. Xamarin displays a dialog box titled "Unhandled Activation Error" with the text "There was an internal error in the activation system. Please contact Xamarin Support with the following error information."

System.Net.WebException: The remote server returned an error: (401) Unauthorized. at System.Net.HttpWebRequest.GetResponse() at Xamarin.Components.Ide.Web.RequestHelper.GetResponse(Func1 createRequest, Action1 prepareRequest, CancellationToken token) at Xamarin.Components.Ide.SSO.Client.DoRequest(String endpoint, String method, String body, CancellationToken cancellationToken) at Xamarin.Components.Ide.SSO.Client.CreateToken(String email, String password, CancellationToken cancellationToken) at Xamarin.Components.Ide.SSO.Client.<>c__DisplayClass5.b__4() at System.Threading.Tasks.Task`1.InnerInvoke() at System.Threading.Tasks.Task.Execute()

Here is what I know that might help: - Windows 7, 64-bit. VS 2010, 2012, and 2013 Update 1 installed. 12GB RAM. - The corporate network uses a proxy server - The corporate proxy servers do a MITM attack on secure connections and present a fake certificate, which is added to the trusted certificate store on our machines.

Is it possible that the second dialog that pops up in step 3 really wants my domain credentials? But that is strange and I do not want to enter them and risk sending them outside the network. Windows should automatically provide those credentials when an application connects to the proxy server. In no other case have I ever been asked for those credentials.

I attached screen shots showing the process.