Same here, GSX has broken after the latest update.
I just ran the updater to 3.1.6 and I'm having the exact same issue. Couatl not launching and GSX not loading in the sim (Never ending "Waiting for Couatl Scipting Engine to start"). Trying to launch it manually in the Addon Manager/couatl64 folder gives me an error "The file or directory is corrupted and unreadable".
I was previously on 3.1.3 and everything was working just fine. Ran the update and it's no longer working. GSX is already excluded in all antivirus and firewall settings.
Sorry to say it, but something is not right about this update - I've used GSX since release and never had any kind of major issue in MSFS until this right now.