Why are the download keys not generated when a customer places an order?

If download keys are not being generated it is usually caused by one of the following:

1. The order isn't processed. The download keys will not be generated until the order is set to processed. If you are manually processing orders be sure to first set the order to processed before it is set to complete.
2. The downloads aren't setup for this particular product or variant.
3. The installation changes to the include/func/func.order.php file are in the incorrect place or haven't been completed.