The Islander just uses the X-Plane engine model, there shouldn't be anything on our end that could stop this (unless Gizmo is not activating the plane, I would need to see the log.txt to know). You can try deleting the file "BN-2B Islander_prefs.txt" in the main Islander folder, and "persist.cfg" and "settings.cfg" in Islander plugins/is_systems/settings. These should reset the plane to the as-installed condition.