How to display custom error message when submitting termination

Summary:

I created a custom error message, but it doesn't display when termination is submitted.

Content (please ensure you mask any confidential information):

We want termination to error and display the custom message when "Last Day Worked" is past termination date. I created a custom error message, but it doesn't work.

Version (include the version you are using, if applicable):

24C

Code Snippet (add any code snippets that support your topic, if applicable):