A user is on a SharePoint site that is running Visio Services in Microsoft SharePoint Server 2010. When the user tries to access the Status page of a workflow site, the user receives the following error message:
Visio Services was unable to load this diagram because the diagram URL does not refer to an existing VDW file or you do not have permissions to access it. To resolve this issue verify that the diagram URL refers to an existing VDW file that you can access.
This issue may occur because the workflow is running on the sub Web level. However, the user does not have permission on the root site.
To resolve this issue as an administrator, grant users View permissions on the root site of the sub Web.