No suitable IPSec-SA found by spi - FortiClient VPN with FotiGate 80E MacOS VPN issues

[elsevero]

Hi there,

I am facing some issues with my FortiGate 80E at some of my clients. I did the config properly since the VPN works fine on Windows machine and even more strange that I have another two FortiGate 80Es and both of them are working properly, no issues with that.

The only log recored that I guest it stands out its: 

20201229 16:56:13.684 [fct_tunnel_ctl:DEBG] udptunnel:254 outbound: No suitable IPSec-SA found by spi: 3476052705. family:2

  I am using FortiClient VPN 6.4.1.1267. As for the FortiGate 80E firmware version I'd update the post later today when I'd have access to the remote office.   Did anyone faced this issue before? How It was solved?