I had the same problem.
Just re-instal.
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READ CAREFULLY. IF YOU DO WRONG YOU COULD LOSE YOUR ADD-ONS AND/OR YOUR SAVES.<===
1: Copy and paste your "Add-Ons" folder and you "Saves" folder to your desktop(only if you don't want to lose them.)
2: Download and instal Blockland.
3: Go to the
key recovery page and follow those steps to get your key.
4: Open your Blocklnad main folder and Copy and Paste your old "Add-Ons" and "Saves" folder into the new Blockland folder, a box should pop-up saying
A folder with this name already exists in this folder. Do you wan't to replace it?
click "Replace" then click "Replace" again.
5: Open you newly installed Blockland game, choose your proxy settings, and copy and paste your key into the box.
The decal problem should now be fixed!