It only displays the controllers that have been active in the last 90 days.
One of the best ways to learn how to communicate to ATC is by asking questions and asking for feedback from the controllers directly. You’ll learn things you may have never known when you message the controller.
So if you need or want to contact a controller, go there. Click the controller’s IFC link and message them on the forum. All of the controllers are active on the forum and answer their messages.