The Jive CTI widget does not work like a soft phone. When you initiate a call from Salesforce, it first sends the call to your Jive phone, waits for you to pick it up, and then finally completes the call to the outbound number.
From the widget (top of the left sidebar):
Enter an extension or 10-digit number.
Click [Dial] to initiate the call from your phone.
Click to Call
Click on any number within Salesforce to add it to the dial field