@arturocivit, Thank you for reaching out.?
I suspect that there might be a plugin conflict causing the issue, therefore, I would suggest disabling all other plugins except for Wordfence and Google Site Kit, then trying again. If that doesn’t work, you could also try to revert to a default theme, such as Twenty Twenty-Three, to confirm whether the google site kit works as expected.
If there’s a plugin or theme conflict, I would suggest changing the Wordfence Web Application Firewall into Learning Mode. From the Wordfence Dashboard, click on Manage WAF. Then you will see Basic Firewall Options > Web Application Firewall Status. Change the option to Learning Mode. Now confirm that the google site kit works as expected. Once done, switch the WAF from Learning Mode back to Enabled and Protecting and test to see whether it works well.
https://www.wordfence.com/help/firewall/learning-mode/ is an amazing resource for learning more about the WAF and learning mode.
Let me know in case the above doesn’t solve your issue.
Thanks,
Mark.