FortiGate to Vyatta - ESP Error

[AK_47]

I'm trying to replace existing pfSense firewall with FortiGate.

All VPN related config was replicated but facing the issue with establishing VPN.

In pfSense under Phase 2 section there is an option Protocol - ESP which I can't see in the Fortigate.

Now under Log & Reports \ VPN Events I can see IPSec ESp related errors - esp_error.

If that related to the overall fail to bring up IPSec VPN tunnel, please advise what should be done to resolve it.

Thank you.