What do I do if a buyer cannot download the file?
Updated
Check the obvious three first
When a buyer cannot download the file, check three things first: the email went to spam, the buyer mistyped their address at checkout, or the link expired before they opened it. Those cover most cases. Resend the link straight away, then fix whatever caused it.
Ask about all three in your first reply. It saves a day of back and forth.
Then check the device
ZIP files on older phones, missing software for a specialist format, or a work network blocking the download.
Ask what device they are on. That usually identifies the problem in one message.
Fix it fast, then fix the cause
Resend the link or send the file directly, quickly and without argument. The speed of your reply is what they will remember.
Then change whatever caused it: a longer expiry, a clearer confirmation page, a plain PDF alongside the ZIP.
Prevent most of it
Show the download on the confirmation page as well as in the email. Add a "resend my download" form.
Those two changes remove most download support messages permanently.