I have this same problem with Ventura 13.4.1 (c), but only when Machine Authentication is set to "Certificate". The connection disconnects immediately with "The L2TP-VPN server did not respond." Because it's immediate, clearly it did not time out waiting for a response. I can see in Wireshark and the remote system's logs that it did respond. But in the Mac's logs I see "IPSec connection failed" as above.
Shared secret authentication (pre shared key) works fine, so I think this is to do with certificates. Perhaps racoon has a problem accessing the system keychain? Or I failed to add the "correct" certificate to authenticate/authenticate to the peer, or to set its trust correctly?
qris
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