It's not clear from your message if the whole Couatl menu disappeared (as you said in the first part of your sentence) or, after reinstalling the "latest update" (which is not clear what it means: the latest Live Update, the latest Stand-Alone Addon Manager or the latest GSX installer ? ), you are now missing JUST the GSX menu.
Please clarify your situation, what you installed, and what you are missing, exactly.