I have found that if my workflow for a support incident assigns a ticket to a reporter (i.e. someone who ONLY has portal access, and does not have a Jira license), then customer notifications stop working entirely until the assignee changes back to a user with a Jira license (one of our service desk agents).
For example, when we find we need more information from the customer, we move the status from Assigned to Pending. At that point the SLA pauses, and it becomes a customer (reporter) action to respond. So it makes logical sense (to me!) to have the workflow assign the ticket to the customer (reporter). But if the workflow does that, the customer does not get a customer notification that the status changed to Pending.
I have noticed that as soon as the assignee changes back to a service desk agent (with Jira license), the customer notifications to the customer (reporter) work just fine on status change or any other condition as configured in Customer Notifications.
A nice side effect of assigning tickets to a customer (reporter) is that they show up on the Service Desk board under the list of assignees, making it easy to filter on a particular customer, to see what is in their "action" queue.
So my question is this: why does assigning a ticket to a customer (reporter) who has no Jira license seem to prevent a customer notification of the change in status?