ContactId from a contact using API - XM directory

Hello! I’m trying to extract a list of contacts from a XM directory, using the "list-directory-contacts" API function. I don't get an error, but it returns "elements": []. In other XM directories the "list-directory-contacts" API does work, and returns all contacts. But in this specific directory, it does not return the contacts (there are only 2). In reality, I need is to get the ContactId of these contacts. Is there another way to recover them? Thank you!