You have a coaching page enabled on the ProxySG (Notify User)
You cannot load the help pages from within Microsoft Office.
During loading of the help files, you are prompted to 'Accept' the notify page.
After accepting the Notify page, you are receiving the error message: Request Error (invalid_request)
Your request could not be processed. Either 'deny' or 'exception' was matched in policy. This could be caused by a mis-configuration, or possibly a malformed request
After clicking Accept during the notify process, Microsoft Office loads a new web browser window. When this occurs, the "Referer" header is lost, which is required for the 'Notify User' process to complete successfully: