I recently had a problem where a customer’s FortiAP 221C AP’s would intermittently stop broadcasting the SSID’s assigned to the 5Ghz Radio.
I had a look at the FortiAP profiles and saw that all channels were selected, including channels 149, 153, 157, 161 and 165. I deselected those so that my configuration was as per below:
Once I did that the AP’s started broadcasting on 5Ghz again. Not sure yet if this is a regulatory limitation due to my country code (ZA) or a bug.