Powershell – Azure Cmdlet Add-AzureRmAccount not working over corporate line

I'm currently learning how to create azure environments using powershell Resource Management cmdlets.
The classic way of working had no problems, I could use Add-AzureAccount and it would allow me to access my subscriptions.

However, with the new Resource Manager cmdlets, when I use Add-AzureRmAccount I get either one of two errrors.

When using stored credentials using $Cred = Get-Credentials, and then logging in using Add-AzureRmAccount -Credential $cred I receive the following error:

Accessing ws metadata exchange failed.

When using the login prompt. Which means I just type in Add-AzureRmAccount and it forwards me to my company SSO page. In which I log in successfully. I get the following error:

An error occurred while sending the request.

When I tried to use the cmdlet from home, using vpn to connect with the same laptop that I was using before. I can connect perfectly using Add-AzureRmAccount and following the logon prompts. Using the stored $credentials still fails with the metadata exchange error.

I'm assuming that the stored credentials method is failing because it can't redirect to the SSO without the interactive prompt.
However I'm unsure what might be causing the interactive logon to fail, as I can clearly reach the SSO, and the Add-AzureAccount cmdlet works on the same machine.

What is the difference between the Add-AzureAccount and the Add-AzureRmAccount cmdlets that might be causing this?

UPDATE:

The full stack trace error is:

Message        : An error occurred while sending the request.
Data           : {}
InnerException : System.Net.WebException: The remote server returned an error: (407) Proxy Authentication Required.
                    at System.Net.HttpWebRequest.EndGetResponse(IAsyncResult asyncResult)
                    at System.Net.Http.HttpClientHandler.GetResponseCallback(IAsyncResult ar)
TargetSite     : Void ThrowForNonSuccess(System.Threading.Tasks.Task)
StackTrace     :    at Microsoft.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
                    at Microsoft.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccess(Task task)
                    at Microsoft.Azure.Subscriptions.TenantOperationsExtensions.List(ITenantOperations operations)
                    at Microsoft.Azure.Commands.ResourceManager.Common.RMProfileClient.ListAccountTenants(AzureAccount
                 account, AzureEnvironment environment, SecureString password, ShowDialog promptBehavior)
                    at Microsoft.Azure.Commands.ResourceManager.Common.RMProfileClient.Login(AzureAccount account,
                 AzureEnvironment environment, String tenantId, String subscriptionId, String subscriptionName,
                 SecureString password)
                    at Microsoft.Azure.Commands.Profile.AddAzureRMAccountCommand.ProcessRecord()
                    at System.Management.Automation.Cmdlet.DoProcessRecord()
                    at System.Management.Automation.CommandProcessor.ProcessRecord()
HelpLink       :
Source         : Microsoft.Threading.Tasks
HResult        : -2146233088

It looks like my error is firewall related.
I'm unsure why the one command (Add-AzureRmAccount) encounters the error while the older version (Add-AzureAccount) does not.