I guess by "software delivered" you meant "license delivered", since the software itself can be downloaded. I saw on their web site the following note. Do you use any of those providers?
"Important information to Hotmail®, Outlook®, MSN® and Live® email users
Microsoft's email services are generating a lot of problems by rejecting notifications sent by our licensing system without understandable reasons. This has been forcing us to invest a significant part of our scarce user support resources to solve problems such as users who don't receive their license data, blocked support messages, license management services that cease working, etc.
If you use a Hotmail, Outlook, MSN or Live email account for your commercial license, you probably won't receive our notification emails, including the email with license activation codes and download/installation instructions. That email is sent automatically by our licensing system when you purchase your license, and the information it provides is absolutely necessary to activate and use your license.
Please be advised that, even if you add our corporate email server (pixinsight.com) to your "safe senders list", you'll probably have problems to use your license, now or in the future, since some of our notification messages may be blocked without apparent reason.
If you are a Microsoft email user, we strongly recommend you use a different email address (not on a Microsoft email service) for your commercial license. As two well-known examples, free Gmail and Yahoo email accounts work perfectly with our licensing system. Sorry for the inconvenience."
Checking WAY back... I made the purchase on Feb 28, 2015... I double checked on Mar 2nd, 2018 as I had not received the licensing... I emailed them and on the same day they determined that for some reason, I didn't get the email. That same day, they refunded my $$$, I bought it again and they sent me an email with licensing.
For some reason, AOL blocked the first email as they are auto generated upon receipt of payment.
My 2 cents.