Switched off anti virus (AVG), ran "Couatl_Updater.exe" (D:\Program Files\Microsoft Games\Microsoft Flight Simulator X\fsdreamteam\couatl).
Are you using an old version (pre-2017) of the GSX installer, which used to install INTO the sim by default, or you explicitly override the default installation folder for our software and told it to go into the sim ?
In the first case, use only the latest installer on our site.
If, instead, you DO have the latest installer, but decided to override the default location and tell it to install into the sim, that's not the best choice right now, because we know install OUTSIDE the sim. In this case, Uninstall every FSDT product and
reply YES to the question "Do you want to remove the Addon Manager". This will Undo your previous choice, and will let you to choose the installation folder again on the next reinstall.
Unless you don't have enough space on C:, the suggested location under C:\Program Files (x86)\Addon Manager is the most sensible choice. If your C: drive is a bit low on space, you can install on another drive but, choosing the SIM folder is not usually a good idea so, use D: and will install into D:\Addon Manager, and that's perfectly fine too.