This one drove me quite mad for sometime this evening until I finally got it working thanks to a slight adaptation on the settings posted here

Since my FreePBX box is not behind a NAT I didn’t need to do anything NAT related, I also set the Codec to Accept only G711 Ulaw/Alaw as I prefer audio quality over bandwidth usage and don’t have the required licenses for G729

Basically Outbound calls were working but I couldn’t get Inbound calls to work, It seems what you place in the outbound settings section also has an affect on the inbound calls!  The Symptom I was experiencing was  incoming calls being dropped with a 421 Unauthorized error

 

Outgoing Settings:

host=sipgate.co.uk
fromuser=SIP-ID
secret=SIP-password
disallow=all
allow=alaw&ulaw
context=from-trunk
insecure=very
type=peer
username=SIP-ID

Incoming Settings

secret=SIP-password
type=user
context=from-trunk

Registration

Register String:

SIP-ID:[email protected]/SIP-ID

Note: the “:” between the SIP-ID and password should be included e.g 123456:[email protected]/123456

The SIP-ID and SIP-Password should be displayed in your Sipgate control panel