[2019-09-20 18:53:02] VERBOSE[C-0000002d] app_dial.c: Called firstname.lastname@example.org:5083
[2019-09-20 18:53:34] WARNING chan_sip.c: Retransmission timeout reached on transmission
Unfortunately, all that tells us is that Asterisk sent the initial INVITE to the OBi but got no reply.
Assuming that the OBi is really at 192.168.1.11 (can you ping it from the PBX)?, X_UserAgentPort for the SPx in question is really set to 5083 (log into the OBi’s local web page to check), and you don’t have any firewall in between, you’ll have to use debugging tools at one end or the other to see what is going wrong.
In the PBX, at the Asterisk console, type
sip set debug on
and make a failing call attempt. The SIP trace will appear in the Asterisk log (interspersed with the normal entries), so you can see if there is anything wrong with the INVITE.
If you have set any security features in the OBi such as X_AccessList, confirm that they are properly configured.
If after checking the above you still see nothing in OBi’s Call History, use its Syslog and/or X_SipDebugOption to see why it is ignoring or rejecting the INVITEs.