Hi Jason-
Yes, the parent (Projects) needs to exist in order for the children (Project tasks) to exist.
First thing: I would add the Error node to the canvas, to make sure that you see any errors while developing the form.
It might be that the Projects (the first list submit) is failing for some reason. With qRules v4.2, you can configure the command to submit only to one of the lists, and I think that might be a good way to troubleshoot.
You can add the /mappingName parameter to your command, i.e. /mappingName="Project"
This tells qRules to map only to the Project list. If this works, then try /mappingName="ProjectTask" and see if that works as well.
As you do this, look at the Error node for any messages.
Let us know how that goes. Thanks!