I am experiencing the same issue.

I have a c2300 router and I am on "Smart Connect", however; the 5ghz band always drops off about a minute after a reboot.  I have put a few devices within 6 inches of the router and still they only connect to 2.4ghz.   For reference my network has 16 wireless devices and every single one of them are on 2.4ghz.  In fact, using wifi analyzers there is no broadcast of the 5ghz band at all - despite the TPLink tether app (and web broswer) saying that it is enabled, and the LED light on the router saying it is active too.

I don't understand why ithe 5ghz band isn't visible to wifi analyzers and no devices are capable of connecting to it when in "smart connect".

With that said, if I enable ONLY the 5ghz band (ie. disable smart connect and 2.4 ghz) devices do connect fine.  The 5ghz band does not seem to drop in this instance, as I have been connected for hours at a time.

For reference, when doing speed tests on the 5ghz band (when it is the only band broadcasted) I get 120+ mbps.  Using the same device in the same location using the 2.4ghz band I get about 50 mbps, which is less than half.  So this begs the question, why won't smart connect even broadcast the 5 ghz band or change my devices to a faster band to get the best connection?  It certainly feels like a glitch in my opinion based on the firmware.

Note - I am well versed in networking too, and work in IT.

@kvnshffr Disabling the SSID broadcast helped for me, I had a similar issue.

I have the same problem with my VR400 AC1200

@kvnshffr I have an Archer c7 and we can not see the 5 either.  i have no tech knowledge!

@Rantwhy 

Rantwhy wrote

@kvnshffr I have an Archer c7 and we can not see the 5 either.  i have no tech knowledge!

First thing I'd check is IF 'Smart Connect' is enabled in Wireless settings? I ask as that could be the default setting in wireless, as you didn't state if you just got the router or if 5Ghz was visible before and now disappeared?