In the form data sources, find the QdabraRules data source. Drag it onto your form and preview. Type a simple command in the Command field - like GenerateGuid - and tab out. The command field should clear and you should have a GUID in the result field.
Sometimes people accidentally add code to their form and disable qRules. If your trial has expired, you should get a message in the error node about that. But if you have just accidentally disabled it by adding code to your form, let me know and I'll help you get back up and running.