Hi Sebastien,
I've responded to your ticket and I guess you didn't receive the response yet? If that's the case, I will help you here.
First off, do you see the Volanta Plugin within the XP plugin's folder?
If you do, please manually delete it and re-launch Volanta. Let Volanta detect and re-install the plugin.
Launch X-plane and load a random flight. Let me know if you see the green icon (Active State).
Thank you,