2.2.6 <-> 2.3.x IPSEC - "no IKE config found for", "sending NO_PROPOSAL_CHOSEN"

[breakaway]

I have a 2.2.6 installation at a remote site and a 2.3.1 in our lab.

I've had a stable IPSEC running between the two. A few days ago I found that IPSEC was dropping, and I couldn't get it to reconnect in the normal way. I even tried rebooting the 2.3.1 in the lab (at that time it was 2.3 release, now running 2.3.1 as of a few minutes ago).

The only "fix" to bring back the VPN connection is to reboot the 2.2.6 instance router.

Logs are attached. As are screenshots of the IPSEC setup page.

[jimp]

Turn up the logging on both sides as detailed here: https://doc.pfsense.org/index.php/IPsec_Troubleshooting#Common_Errors_.28strongSwan.2C_pfSense_.3E.3D_2.2.x.29

Usually that would mean either there is a mismatch or it's not matching the connection properly (remote gateway and identifier are not matching)