Azure: You do not have any subscriptions in the directory

In the classic portal (https://manage.windowsazure.com), adding you as a co-administrator is enough to give you full access to the subscription.

However, in the new portal (https://portal.azure.com), you should be added as a Co-Owner through the RBAC system. Someone with an appropriate role should go to Browse > Subscriptions > "subscription_name" > All settings > Users to add you with the Owner role for example.

Does it help?