We don't have any way for users to reactivate their own expired download links; there just hasn't been much demand for such a feature that would justify the major investment to develop it. Fortunately, we have at least added a new Reactivate Links button in your Transaction Log, so you don't have to copy and paste Transaction IDs anymore; you can just find the buyer's sale in your log and click the button to reactive their links.
If you're having to reactivate links frequently for current buyers, your link expiration settings may be too restrictive. You want a balance that lets the vast majority of buyers complete their download without needing to contact you, while limiting potential theft from link-sharing. I reviewed your expiry settings, which seem generally reasonable for typical small files, but you might consider expanding the Attempts limit and restricting the Hours, especially for products that you notice buyers most often have trouble with (perhaps items issuing extremely large files?).
One common download issue we see affects Apple iOS mobile devices, as the default Safari browser in iOS will only download a file if the device has an app installed that can open that filetype -- e.g., it won't download a ZIP file unless the user has already installed an app that can open ZIP files. You might add a notice to these buyers in the Product Thank-you Page HTML field of your products' settings, like so:
<p><b>Apple iPhone/iPad/iPod users:</b>
This is a <b>ZIP</b> file download. Make
sure you have an app installed that can open
<b>ZIP</b> files before you try downloading
this file to your device, or you can just
download it to your regular desktop/laptop
computer using the link we emailed you.</p>
You might even review free ZIP apps available for iOS and provide a link there to one you'd recommend.
If all of your files are ZIPs, you could also just put this notice in your Common Thank-you Page HTML field (in Seller Admin under Manage Seller Account > Edit Preferences), which would spare you the effort of having to paste it into each product's settings.
