One possibility is that you misspelled the email, so do check that.
Otherwise we can check if you contact support if it has been properly sent and accepted by the recipients email server.
Finally, the user can trigger a re-send by registering manually at the web site, https://www.axcrypt.net/ . Of course – if you’ve shared the file with the wrong e-mail address the user will not be able to open the file anyway.
Also, please remember – we do *not* send the actual files, it’s not quite clear from your post, but you do need to send the actual files separately yourself.