Nighthawk AC1900 5GHz Channel stopped working

I got the router in December 2015 and has been working flawlessly.  I've usually had 3 devices on the 5GHz network, and 3 on the 2.4GHz.  A couple days ago the 5GHz stopped working.  No devices can connect to it.  On the admin screen it shows nothing wrong, and there's nothing in the logs.  In addition to that, anything that connects now will only do 54Mbps max.   It's still set to 1300 on 5GHz, and 600Mbps on the 2.4.  I've installed the latest firmware, that didn't fix it.  Looks like I need a hardware replacement.  

Any advice?

Thanks,

Kevin