What's wrong with the custom field?

Question

WordPress

hello!
I work with wpadverts bulletin board plugin.
the task is to add one field to the form for adding ads.
did as it is written in the documentation https://wpadverts.com/documentation/custom-fields/
as a result: my field appeared in the form, the data from it on the ad page is displayed without problems, but for some reason they do not participate in the site search.
help me figure it out please!