How are you opening the GC line device handle in this case?
Are you creating a full duplex route between the GC and voice devices?
Make sure you also have correct IP address selected in the CLI interface for RTP streaming if on a multiple NIC system.
The error above has to due with what is passed for codec capabilities for that specific channel (meaning how IP_CAPABILITY structure is set) after its open. This must match the feature set residing in the license. Thus if you use the DONTCARE parameter for codec used and, but you only have basic RTP and not enhanced RTP port in the license the error will show up.
Jeff