If the UnicastBridgeControl - ERROR: CcSetup/Conference failed- not enough streams or bandwidth available error is found in the Cisco CallManager traces, it means that the phone had a location built with less bandwidth. In this case, only a limited number of calls can be brought into the conference. Once the limit is reached, all the other calls fail to join the conference.
To resolve this issue, increase the bandwidth as needed based on the availability and the requirements for the number of connections in the conference call.
If you have given a bandwidth limit in the location configuration setting of the phone, and if the call bandwidth exceeds this configured limit, the conferencing will fail. In order to resolve this issue, configure Unlimited Bandwidth in the Phone Location Configuration Settings.