Custom social icons background hover color

Dear support,
I have a custom social icon in the top left header, together some standard Enfold social icons.
Thanks to your suggestions, I have successfully changed the background hover color (when the mouse hover the icon), in my case orange. Now, with the latest theme updates the background color doesn’t seem to work anymore.
I added this line to the file style.css in the Enfold child theme:

#top .social_bookmarks_issuu:hover a{color:#fff; background-color:#ff6600; }

now changing “color:” does work, but changing “background-color:” doesn’t work. Any suggestion how to restore the functionality?

Thank you
Guido