OpenHab2 Problems with NTP binding installation

I start today with openhab2 and i wanna say to you that is amazing guys!!! Compliments to all the contributors.

Anyway, I wanna ask you something about NTP binding, that in my case seems binding installation don’t want do start.
from logger i recive:
Adding add-on ‘openhab-binding-ntp’ failed: Permesso negato

Can you help me to understand the problem? Thank you .