1) Go to Central Administration | Application Management | Manage service applications | Visio Graphics Service | Global Settings
2) Check the Application ID under Unattended Service Account
3) You should have entered an application Id here, if not create a Secure Store Target Application of type Group and then enter its Target Application ID for Visio Graphics Account.
To create a new secure store target application go to Central Administration | Application Management | Manage service applications | Secure Store Service