Scheduled Actions on Process Builder are not invoked

Question

I have created a process builder for sending email alerts 30 days before a date field on a record.

So I have added a criteria for activating only when the status__c field equals scheduled.

Then I have added Scheduled Actions to it - to send an email 30 days before the due_date__c field value.

For enabling Scheduled Actions I had to mark in the criteria, this section as true:

Do you want to execute the actions only when specified changes are made to the record

But because of that, this criteria does not always happen

My main use case is - if the status__c field does not change, and the due_date__c field only changes - then the schedule does not happen.

I have tried to add ISCHANGED to the due_date__c field to the criteria but that is not allowed.

Is there any way to trigger the Scheduled Actions always when the due_date__c field changes?

Here is a snap of my process:

UPDATE

The error when adding IS CHANGED to the due_date__c field:

Answer 1

So when you select yes when prompted "Do you want to execute the actions only when specified changes are made to the record?"(thus allowing you to create a scheduled action) you are only going to fire the event when you make a change and it explicitly makes all rule criteria true.

The reason you cannot use ISCHANGED is how scheduled actions work. At the time scheduled, if the rule criteria still evaluates to true, then the action will fire, which means that in order to use ISCHANGED, you would have to store the prior value of the field until at least the scheduled action executes - expensive and not supported.

I would recommend making your second rule criteria due_date__c Not Equal to GlobalConstants.Null

This will allow your scheduled action to be scheduled upon change of due date. It will also allow the action to be scheduled in the case where the status__c is populated but the due_date__c is not.