Hi David,
Can you try the following:
-Import a fresh copy of the sandbox into Virtualbox (highly advisable to up the memory of the VM to at least 6-8GB)
-Point your browser to: http://127.0.0.1:8000
-Click on the Ambari ‘Enable’ button
-Point your browser to http://127.0.0.1:8080
-Login with admin/admin
Hope that helps,
Darwin