The above log format is Fortinet native log format where date and time fields are separated. It does not comply to the WELF format. Hence Firewall Analyzer is unable to process this log.
Kindly enable Web Trends check box in Fortinet logging configuration if you are having Forinet family firewalls and you can see Firewall Analyzer showing reports for Fortinet firewalls.
Following are the details steps,
1) Login as admin to fortinet
2) Click "Log & Report" ----> Click "Log Config"
3) Once you clicked "Log Config", settings of "Log Settings' tab 'll be displayed. Here you can enable "Web Trends".