Here are 3 important configuration rules for ISSABEL call center
The agent extension MUST BE FOUR (4) digits.
2 ( A ) AGENT MODE:
The agents in your STATIC AGENTS box in the QUEUE menu in the PBX GUI must contain the AGENT NUMBER you assign.
...then in the QUEUE it MUST HAVE an "A" in front of it.
2( B ) CALL BACK MODE
The extension that you are assigning in the queue in DYNAMIC MEMBERS -must- contain an "S" in front of the number, assuming its SIP extension.
3>WAIT one (1) minute after you configure new agents before testing. There is some sort of process in ISSABEL I think that doesn't always let a new agent work right away. Wait 1 minute between changes to ensure your configuration changes were applied by the system.
This might help: