Core Issue
This is an example of the issue that occurs in the Cisco CallManager 4.x, and Cisco CallManager 5.x:
In a call between A and B, B can conference in a third participant, C, but when C tries to conference in another participant, the IP Phone of C displays the Key not active error message, and it does not allow C to add another participant.
Note: This issue does not occur in Cisco CallManager 4.2(3).
Resolution
There are two types of ad hoc conferences, Basic and Advanced. In basic ad hoc conferences, the originator of the conference acts as the controller of the conference and is the only participant who can add or remove other participants.
In advanced ad hoc conferences, any participant can add or remove other participants. This capability is not limited to the originator of the conference. Advanced ad hoc conferences also allow multiple ad hoc conferences to be linked together.
Advanced ad hoc conferences are only available in the Cisco CallManager 4.2(3). In order to enable advanced ad hoc conferences, set the Advanced Ad Hoc Conference Enabled clusterwide service parameter to True.
Refer to the Conference Bridges section of Cisco Unified CallManager System Guide, Release 4.2(3) for more information.