Because Blockland is now in a new directory location. or just download them all again.
Odd, my addons were copied in automatically. It should have done that for you. Did you hit "no" to something that came up regarding addons?
Go to your old Blockland folder, copy all your old add ons. Go to My documents/Blockland/Add-ons, paste paste your add-ons.Run the launcher.Sit down.Shut up.
Run the launcher.Sit down.Shut up.