Netgen Gallery with Photon

I use Jetpack Photon feature but it seems not to work with Nextegen Gallery images (see http://www.georgsoltiaccademia.org/castiglion-della-pescaia/ for example).
I also installed CDN-Powered NextGEN Galleries with Jetpack Photon plugin but it seems to do nothing, images are stil served by mys erver.
Any idea to solve?

Thanks

Simone

https://wordpress.org/plugins/nextgen-gallery/