Hi Vic,
I apologize for not noticing this question until now. If you still have this question, the most common cause for this message is that you have chosen a resource field that was not populated before the process was run. If it is not populated, there is no one for the process to send the notification to. Once you get this error, you can fill in that field with whoever you want to be notified, then go to the messages for the process and retry the step.
Let me know whether or not this resolves your problem.
Sincerely yours,
Jeanne Gaskill
Senior Support Engineer