Hello, Fernando Ugarte,
Thank you for purchasing our theme and for reaching out to our support center.
In order to resolve your issue, please rename the xstore-es.po and xstore-es.mo files to xstore-es_ES.po and xstore-es_ES.mo, respectively, as shown in the screenshot provided: https://prnt.sc/7Zd3Se6wlzIR.
You have selected the correct System location for the files. Even if you are using a child theme, you will still need to translate the parent theme.
For more information, please refer to our theme documentation here: https://xstore.helpscoutdocs.com/article/103-translation-files-update.
If you have any further questions or concerns, please do not hesitate to contact us. Our support team is always available to help.
Best Regards,
8Themes Team