Re: Authentication Fortinet Single Sign-On (FSSO) in MACOS HIGH SIERRA
your initial screenshot points more towards SSL cert issues, probably due to deep inspection.
If you resolved that and your MAC is inside domain, but your AD logon is not seen in FSSO on FGT, like in 'diag debug auth fsso list' , or in firewall (this part is checked in policies) ' diag fire auth list'.
Then it might be caused by FGT not knowing about your user from FSSO.
Check if you do have connected Collector agent via ..
diag debug en
diag debug authd fsso server-status
Also, standalone collector is able to set which logon events it is processing. As during logon to domain there is whole lot of events, like 15, and for FSSO is useful just one or two of those.
In the past I seen that MacOS computers generated 4624 EventId types during their authentication to domain.
Therefore make sure your standalone collector has Advanced Settings > General > Windows Security Event Logs > Event IDs to poll = "2".
If you not have standalone collector, usual and cheapest way, then maybe let us know with more details about your setup.