Could you send a picture of the setup you have on your reference selector? at first glance, my guess would be that you have the display attribute as a null field for the entity. For example, when I set up a reference selector in a recent project of mine I did the following:
So if you picked a different field inside of your entity that is empty inside your database, it will show up but with no display value. If that is not the case, I would check the access rules, but that would give you no results and is unlikely