I am having this same problem all of a sudden! My 5Ghz SSID is no longer broadcasting. I tried upgrading the firmware to a new version 3.201 but that did not solve the problem.
To be clear, it was working and randomly stopped. I hadn’t changed any settings or logged into the router in weeks. No matter what I try, I can’t get it to broadcast 5Ghz even though it says it is. Please help!