What I see is that it redirects me to the WordPress homepage, but since my WP installation is in a subfolder (for security reasons) I suppose it redirects me to the wrong page. Can you let me know whare I should change the code so that it works?
Stefano, you’ve been great with your help! Thank you!
It seems the issue was WordPress Firewall, which blocked the Save / Send requests as suspicious requests. I usually don’t get that issue, because I whitelist my IP address from the Firewall plugin settings, but in this case I had forgotten to do so.