Supposing we have the following Scenario:
User 1 has delegated access to User 2.
User 2 is the Owner of Document A.
Both users are registered for Single Sign-On in Office 365 and the Vault uses MS Office Collaborative Authoring.
When User 1 logs in as a delegate for User 2 and uses the "Edit in Microsoft Office" action for Document A, MS Office requests user log-in details (which User 1 provides) but then reports an "Access Denied" Sharepoint error.
The question is if the error is expected in this case.
The error is expected in this case.
if the user who has been delegated the task has not already accessed the document from their own account (thus getting access on Sharepoint), they will not be allowed to access it through a delegated account.
Vault Help Documentation: