Your screenshot is not very useful, since it shows the Addon manager folder, which will never fail to install. What might fail, is the linking to the MSFS Community folder, which usually happens if you copied the installation there manually, maybe even a long while ago.
So you need to check the two GSX packages in the Community folder, and if you see they are not links ( normal ) but are real folders instead ( wrong, because of they were manually copied ), you must REMOVE the real folders, start the FSDT Installer again, and choose RELINK, so it will recreate the linked folders, which is the normal install.
You a recognize if a folder is a link or a real folder by the presence of a very small arrow (shortcut) symbol on the folder icon. The correct situation is that *both* packages must be links, and if they are not, remove them and Relink.
