SIP help

Hi, i was using an older version of asterisk 1.8.0 and now i am using the latest but now when i press the Xfer button in my office IP phone SPA921 (Linksys) and i transfer the call to another party, the called party rings but the calle is in silent, NO Ring Ring… tone and that was working fine in the version 1.8.0, now NOT, what have change?