For the business rule to trigger, the date for which the alert is scheduled must in fact be in the future (as the notification engine cannot time travel to the past), but I reckon that may not be your point.

The business rule looks alright (bit too strict if you ask me), but in your then clause you may wish to add the parameter that removes old versions of the alert (as the employee could otherwise get double or outdated notifications).

The problem with finding a resolution here is however on several levels:
1. The effective date of the rule. If the rule started late, then that could be a reason that certain alerts were not triggered.
2. Application of the rule --> If the rule was implemented later, the Save of Job Info records will not have caused an alert to be stored and that could be a reason for some to be lacking.
3. The criteria in your IF clause could be too strict. The criteria for the contract end date that needs to change (as especially with the new parameter that may not even be needed anymore) could have blocked some and the requirements for the event date could also have blocked it dependent on the first moment of execution / application in general of the business rule.

As we cannot see all the context, it's hard to say which reason is applicable, but either 1 of these things will likely be the case.