After publish website, plugin don’t save anymore

Hi guys,
hope to find help in here,

I just publish my website, doing that I changed few fields in the database, and I’m afraid I changed the plugin configuration.

Once I change the CSS code on the plugin interface and I click on “SAVE CSS” page not found appears and the url is set as “https://www.sgden.org.uk/wp-admin/options.php”.
Basically the plugin instead of save the file takes me to https://www.sgden.org.uk/wp-admin/options.php

Any idea?

Thanks in advance!!!

Marcello