I've been testing 3CX and have a problem that seems it might be an error in a 3CX Invite, or a configuration issue. I have two SPA941 phones configured as extensions in 3CX. I also have a Dialogic DMG2000 configured as a PSTN gateway that is connected to our PBX. Calls between the PBX and the SPA941 extensions through the PSTN gateway work fine. I tried a test of calling from one SPA941 to the second SPA941 and then transferring that call from the second SPA941 out the PSTN gateway. While the connection between 3CX and the gateway is fine (the PBX station answers the ring), when 3CX does the Invite back to the originating SPA941 to complete the connection, the Invite does not have any Media Description in the SIP message body, so the SPA941 responds back to 3CX with "488 Not Acceptable Here" and "Warning: 304 spa "Media type not available"". Does anyone know how to correct this failure?