File won't 'Unblock'.

[Guest Mudbox]

I downloaded a plugin for Paint.net into the 'effects' folder and I

click on 'properties' and then click 'unblock' and 'apply' , and then

'ok', but the 'effects' menu on the paint program doesn't show the new

program in the menu, and when I go back to look at the file, it is still

blocked.

 

I can't unblock the file.

 

What will unblock it?

 

 

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Mudbox