If your device has a lower firmware version then you can enable System Logs by first upgrading your firmware. Next, you need to follow the steps given below.
This applicable for all GEN6, Gen7, and GEN8 firewalls.
To enable system logs
Reconfigure Reporting and Analytics.
There may be momentary loss of data in the firewall while reconfiguring reporting and analytics.
Check if the flow log transport mechanism has changed from VPN to Encrypted mode after the reporting and analytics is reconfigured. If it is changed successfully, the system will disable the SGMSServer-VPN tunnel that is established to transfer flow logs to NSM and you should not enable this tunnel manually.
Once you have successfully completed all the steps, you will be able to view the System Logs option in the Monitor View of the firewall.