I'm sorry, I did omit a lot of information.
1. Yes, the appliance is locally managed.
2. NAT is disable for this site
3. Local encryption domain is manually set for 3 internal networks, which obviously does not include the cluster SYNC network.
4. The connections times out, zdebug shows:
;[cpu_0];[fw4_0];fw_log_drop_ex: Packet proto=1 10.231.149.2:2048 -> 172.16.1.2:29833 dropped by vpn_encrypt_chain Reason: No error;
10.231.149.2 is the sync IP address and 172.16.1.2 is the host in the remote site.
5. Peers are AWS and Azure. I do not think there is any issue there. The packet simply won't get there, since the GW is using an IP that is not (and should not be) in the encryption domain.
Mainly, my question is: can I make the 1400 use an internal IP from a network that is in the encryption domain or do I have to redo all VPN site configs to include the SYNC network? (including AWS and Azure gws configs)