Dale,
Looks like the SRX is not getting a response from the remote side after transitioning to port 4500 due to a NAT device in the path. it is timig out the phase 1 negotiation after a few attempts.
Please check if the remote side is responding to the SRX's requests on port 4500.
Also check if you have a firewall filter on the external/loopback interface which is blocking UDP 4500 replies.
Regards,
Sahil Sharma
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