Download result for MS Edge and Internet Explorer code in page

When I am viewing my page with the embedded Excel file in MS Edge or Internet Explorer and click the “Download” link a page with the characters in the file appears instead of the formatted Excel file. When I try this on our dev site that is on https this doesn’t happen – i.e. I’m prompted to either open or download the file.
Is there anything I can do to fix the issue on our site that is not on https? Any code I can add or any workaround?

The page I need help with: [log in to see the link]