To resolve the problem of the MD-11 Installer not detecting your MSFS install please follow the steps below:
1) Please Right click MD11InstallManager executable -> "Show More Options" -> "Create Shortcut"
2) Right-click the new shortcut -> Properties. This will take you to the menu shown below:
3) Add /msfs="YOUR COMMUNITY FOLDER PATH" to the Target value and press “OK”
4) Run the NEW Shortcut to the MD-11 Installer.
If the issue still persists please create a support ticket.