Hello Jeroen, thank you very much for your answer.
The problem is that I have an installation in English on a bilingual website, so wordpress chooses English as the main language.
I had to translate the parts I needed to display on the web, but it was relatively easy. Ideally, more than one language could be incorporated at the same time in compatibility with plugins like Polylang for multi-language sites.
I will investigate how to collaborate to have the translations into Spanish.
Name Directory is a great plugin, Thank you again for your answers, support and advice.