I just found out that with 5.6 those event categories like WiFi Events, VPN Events, etc. in the GUI is available if remote logging methods are enabled, such as FortiAnalyzer/Manager or FortiCloud. Memory logging doesn't enable the view. Disk logging is no longer available with lower models so that's not an option either.
Do you have "Display Logs From" set to "FortiCloud" at Log Settings? Our 60D we have FortiAP connected still runs 5.4.8 since 5.6 has the zone config issue with vlans. I was checking the GUI menu with another LAB 60D with 5.6.5. So no real log on it.