You may run into error message when trying to access Azure via PowerShell command line such as Get-AzureReservedIP. Error message may say "Your Azure credentials have not been set up or have expired" which indicates that Azure Subscription is not properly authenticated. In our situation, we were trying to use Subscription name that is assigned to other user. You need to make sure that Azure Subscription and User account are properly set.  

You need to change user subscription that belongs to the user or change user that can access subscription. We resolved this error by switching user account via Add-AzureAccount command to a user that had access to our subscription.

Detailed Error Message is shown below.

Get-AzureReservedIP : Your Azure credentials have not been set up or have expired, please run Add-AzureAccount to set
up your Azure credentials.
At line:1 char:1
+ Get-AzureReservedIP
+ ~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : NotSpecified: (:) [Get-AzureReservedIP], ArgumentException
+ FullyQualifiedErrorId : System.ArgumentException,Microsoft.WindowsAzure.Commands.ServiceManagement.IaaS.GetAzure