Overview:

Error: Document Not Found - Occurs after moving a Vault document to a new state and attempting to view the document.

Root Cause:

The Role, to which the user is assigned, does not have View Document permission in the new lifecycle state to which the document is moved.

Solution:

1. Navigate to: Admin --> Configuration --> Document Lifecycle --> [Lifecycle] --> States --> [State]  --> Security. 
2. Grant View Document permission to the Role in which the user is assigned. 

Related Documentation:

Vault Help Documentation: Defining Document Role Permissions (Security Settings)