Excel Data Filter

We had uploaded a few Excel tables with filtered headings about two weeks ago. When we shared the link to them, the public could view them just as we uploaded them and could sort the columns themselves.

All of a sudden this past week, the files no longer have this functionality and are now showing as basically pdf pages, with very small text. No settings were changed on our end, and the file sizes did not increase.

What causes this, and how do we fix it?