Double check your ports you have forward from your router.
Active FTP works but it's not using port 20. You may need to use 20 and 21 for your FTP rule on your router.
Passive FTP not working. Make sure your using the same passive ports on your router that your using for your DiskStation.
Product Model: DS-106
Firmware Version: 2.0.3 - 0640
I have my reasons for my insanity....