We had the same issue too many complaints from our customers. We traced it to the Excel office Security patch KB3115262 - https://support.microsoft.com/en-us/kb/3115262 Which came out July 12, 2016
We asked clients to modify their Excel files to enable files from the internet in order to get around the problem.
(1) Launch Excel. click on File Options.
2) Select Trust Center Settings under Trust Center.
Three) Select Protected View. Three alternatives are displayed when they were all selected.
The first checkbox, "Enable Protected View for files coming from the Internet," is deactivated.
That resolved the problem. Possibly not the finest choice. I'm not sure why this specific KB ruined it, but I wonder whether it has something to do with the fact that the file format is unexpected and this setting is in a clash with it.
All of those are tested on a computer I own that doesn't have this KB loaded, and it still functions well (it isn't blank, but it does prompt that the file format is different and, I believe, shows in protected view).
The fact that the file operates normally if we resave it in notepad or notepad++ without making any changes is what convinced us that the problem wasn't with the file's content. Therefore, Excel must be reading a file property rather than the file's content to cause the problem.