{display_name} doesn't work

Hello,

The plugin is working fine except that when I want to change {user_nicename} to {display_name} when searching for authors, it doesn’t work and displays:

{user_nicename}

on the front end results (with the proper {author_link} though)

Where could it come from?

Thanks.

https://www.ads-software.com/plugins/ajaxy-search-form/