Symptoms
During a workflow if you have for instance a client event that has are four possible outcomes and that the client events loop back on themselves then certain tasks may not be generated. Even though the view flow of the workflow indicates that the workflow is at an email step or other relevant notification step.
Diagnoses
The reason as to why activates are not generated in this scenario is because the activity may be going into an infinite loop. This can happen when you have multiple client events looping back on themselves.
Resolution
To fix this scenario, what you can try is attempt to put another activity in between the point of failure of the workflow by adding a separate step and then having that step loop back to the original step.