Thank you for posting to the Fortinet Community Forum.
You need to have the internet access because your FGT should have connectivity with the FortiGuard server for license update.
For AV,IPS you can directly upload the database by downloading it from support portal.
For registration webfilter,antispam you need to have real time internet access.
Another option is you can use Fortimanager as your Fortiguard server and there should be connectivity between FortiGate and Fortimanager.
Let us know if this helps.
Salon Raj Joshi