I am trying to set up my T42s with a second extension. When I try to provision it via the 3CX UI, I get the message "...belongs to MAC XXX choose another phone/MAC. Phone and 3CX server are both on LAN. I am assuming I need to enable the other "accounts" via the Yealink UI, but when I populate the fields in the Yealink UI with what makes the most sense to me (Port 5062/The register name of the phone, and the username and password for the extenion) I get "register failed" on the Yealink UI. I successfully provisioned Line1 with a different extension and Port (5060).