ATTENTION OTHER USERS: Unfortunately nobody from MacHeist seems interested in chiming in and speaking up on this so-called support forum, however, here is the deal.
Go back and find the original email for your receipt, titled:
Your MacHeist 3 Bundle Receipt
(NOT the email of your serial numbers)
In that, there is a link to view your receipt online, which also includes all the serial numbers. At that link, the serial numbers for iSale that were not generating ARE NOW ACTIVE. If you look in the email of your serial numbers it will obviously still say that the serial number has not generated, so you have to goto view it on the website from the link in the receipt email.
Art Director on Twitter