407 error sbc

Hi, I have a PSTN line connected to an Edgewater SBC FXO port which registers LAN …1.254 as a call Gateway. Incoming calls route ok from GW…1.254 to LAN …1.1 as the LAN GW and out to a FreePBX on …1.4. FreePBX is getting the invite but refusing on 401 Unauthorised. Now my “inexperience”!!! There is no trunk or equivalent setup between FreePBX and …1.1 > 1.254 apart from the trunk to a hosted Sip SERVER, so we just have a routed call coming in from the FXO port. What needs to authorise and how? Please help?