Since we haven't changed anything in GSX either, it's clear that something HAS changed in your system, most likely without your knowing. Most likely an antivirus update. that made the antivirus more bugged than usual, so it decided to mistakely block our software.
- Configure the antivirus to exclude the whole Addon Manager folder.
- Run the FSDT Live Update again.
- If that doesn't work, try do it again, after a Windows restart.