We have found numerous problems users are having with HTML formatted cell data exporting directly into Excel from Project Insight. This is due to a July 2016 Microsoft security update to Excel 2010, 2013 and 2016. The data is in the file, but you cannot see it and the spreadsheet looks empty because the data is blocked. In some cases, all Office programs will warn that the downloaded file may be corrupt, even though it is not. While this problem is most likely identified during an Excel export attempt, it applies to all Microsoft Office files.
The recommended method that works for most organizations is to add your Project Insight URL to your PC's "Internet Options" as a Trusted Site. Once your PI URL has been added as a Trusted Site, test another export to see if the issue with the file being blocked persists. If it is still blocked, please contact your internal IT because a Firewall, Network Security Application and/or Group Policy might also need your PI URL configured as a trusted site.
In addition to the export of reports to Excel, it also affects any file originating from the internet that is opened in a native Microsoft Office file format. Due to this only affecting file types native to the Microsoft Office files, an export to .csv will allow an export of a report to download unblocked since a csv file is an unformatted file type that can be opened by many different programs including Excel.
The user can still save the file and then right-click the file to unblock it in the file properties (right-click the file to get to the properties).
Other options which are not recommended because they can by-pass the vulnerability protection:
Disable Excel's protection for all file downloaded from the internet.
(Excel Options -> Trust Center -> Trust Center Settings -> Protected View - clear the "Enable Protected view for files originating from the Internet" box)
Uninstall the MS Excel Security update (KB3115322) that is causing this issue.
A good reference article from InfoWorld as to what Microsoft has done is located here: