Ive got a trunk up and running, but Im struggling trying to get the MWI notifications to the phone (Freepbx, Asterix 11)

What configs have people use to configure the MWI? I see the UDP NOTIFY packets coming from Voipo and hitting my Asterisk box.
I tried to subscribe to VMail notifications, but Voipo's server is replying with a "Method not allowed", error 405.

Im using Cisco 7970, and apart from the MWI everything is working great.

Any tips?