Forza 6: Apex | Nurburgring DLC itself cannot be purchased

Nurburging DLC is $9.29. However, when I tried to purchase this DLC, a login-dialog popped out and I entered my password into that box. After that, the dialog disappear and the game just died for 2 seconds. Then nothing happened. the Nurburging DLC is still locked and I checked my bank history, it did not charge me anything. Can anyone help me buy this DLC? Or this just a bug of application? Thanks in advance.