Linphone extension status is always OffLine

Hi,
i’m running Linphone Desktop 4.4.8 on Ubuntu pc: everything works fine except the Extension Status that is always OffLine.
On older pc (with Ubuntu) i’m running Linphone 3.12.0 and it works perfectly.
The extensions has the same configuration on FreePbx.

Any advice?
Thanks

You mean the phone works for calling out on, but cannot receive calls since Asterisk sees it offline?