I have a working Azure account with various services already running. I receive monthly bills for these.
Now, I created a workerrole in Visual Studio that I want to
You found the solution to your problem. I had the same symptom, but the solution was another:
You need to go to Extensions and Updates and then update the Microsoft Azure SDK 2.8. After that, I could login and see the subscription (for my case it was a DreamSpark subscription)
This following site, which is about free Azure for DreamSpark (students), actually says that Visual Studio 2013 is not supported, only VS 2015 Community, but it works for me - if I update the Azure SDK as written above. http://blogs.msdn.com/b/microsoft_student_developer_blog/archive/2015/04/09/using-microsoft-azure-for-students.aspx
Microsoft Azure SDK 2.8 (if you cannot find it in Extensions and Updates some time from now): https://azure.microsoft.com/en-us/blog/announcing-the-azure-sdk-2-7-for-net/