“Download” doesn’t work in file browser

My wife has used this plugin on her site for quite some time to allow her clients to upload files. Last night, she tried to download one of the files a client uploaded some time ago, and nothing happens when the “Download” link is clicked in Settings->Iptanus File Upload->File Browser.

I tried it from my computer, and found the same results. I disabled ad and script blocking extensions in Firefox, I even disabled the browser’s built-in tracker protection, and… same result. I also tried it both before and after updating WordPress, so it doesn’t work on either 7.0.4 or 7.1, at least on her site.

I ended up having to connect to my VPS via SFTP and download the file she wanted manually (I’ve since realized that in the separate “Uploaded Files” back-end page, the “open file link” function works, but the “download” icon on that page also does nothing). I have no idea how long it’s been broken, as she hasn’t been primarily using this interface to get files from clients for a year or so (she needed to retrieve an old file).

Since I’m not seeing other support requests for this problem, I’m guessing it’s not universal (and since the files are private, and only available via the admin back-end, I can’t point to a page that demonstrates the problem). Any idea why this wouldn’t be working on her WP 7.1 site?