Thanks for letting us know about this issue. We have done some further debugging and experimenting with that option. We fixed that bug and will soon release an update of the plugin with that correction.
However, there is one not very optimistic note about this. Unfortunately IE still has problem with the displaying the files in browser that were marked as “masked”, so we decided to force users download them when it is discovered that the user browser is IE. Downloading file works just fine.
Also, is it critical for you not displaying files in the browser? If not, then you can use the “force_download” attribute in the our short code with any value, e.g.,
[email-download download_id="4" contact_form_id="4" force_download=”true”]
In this case, the downloading will be force in every browser.