Excel/Word/PPT Macro throws 401/403 errors when trying to fetch the relevant attachments on a page

Issue Summary

MS Office (Word/Excel/ Powerpoint)Macros don't see files attached to the page.

Environment

Both TinyMCE and Fabric

Steps to Reproduce

1. Add an Office file to a Pages
2. Select the appropriate macro.
3. Try to select the file when prompted.

Expected Results

You should be able to see a list of all relevant attachments.

Actual Results

The dropdown list is empty. 401/403 errors can be observed in the Developer Tools Console.

Workaround

The embedded view/preview still works.