Employee ceases to receive Rejection Notification for ICP after element Input Values made mandatory

Summary:

We have a suite of payroll elements used in ICP for Overtime, Additional Hours etc; all the elements have an Input Value 'Reason for Work' which has hitherto been non-mandatory. In most cases the field cannot now be made directly mandatory as element entries already exist where the input value is null, so in order to make them mandatory we've applied an element validation fast formula.
Previously when a Manage Personal Contributions transaction was Rejected by an approver, the employee received a workflow notification to advise them of the fact.
After applying the element validation formula (and where possible making the input value mandatory), no Rejection notification is produced.