I think the issue is having removed SODE manually at some stage. Do you still have the 1.5.3 installer ? It likely came with an addon scenery. If you have it, you might be able to fix it this way:
- Install SODE 1.5.3
- Uninstall it from the Windows Control Panel
- Reinstall the latest SODE 1.6.3 (it's included with GSX, so you can also reinstall GSX).