Do you know if the document is stored in SharePoint, OneDrive or another cloud type service?
If the document is stored in on one of the above systems then you might suggest the user save a copy to the local machine. The user can then Convert to Unformatted Citations and then try to use Update Citations and Bibliography.
The user might also want to try the following steps from the Knowledge Base:
You can also suggest the contact us directly.
Please contact Technical Support directly
1-800-336-4474 option 4 then 1
or
We are here to help whenever you run into issues.