5 GHz Band not available on WIFI settings across all devices connected to my Netgear RAX54 Router

[TERRYNYBERG]

I am using a Netgear- CM1150V modem with ethernet connectivity to a Netgear RAX54 router (firmware is up to date (v1.0.16.132)). My service provider is Xfinity. My devices are connected to the router via WIFI and some are also connected to the router via an ethernet cable (Cat 7). 

The 5 G bandwidth is not available on Wifi settings on any device I use (desktop, portable, iPhones, etc), and does not appear as an item in WIFI settings on any device. Everything currently is connected via the 2.6 GHz band - which is the only option available in the WIFI settings across these devices.

I have rebooted both the modem and router. Xfinity has run diagnostics on both and everything checks out from their end.

How can I restore access to the 5 Ghz band?

[plemans · Accepted solution]

is smart connect enabled? 

https://kb.netgear.com/25346/What-is-Smart-Connect-and-how-do-I-enable-or-disable-it-on-my-Nighthawk...

[FURRYe38]

Try a factory reset and setup from scratch using a wired PC? 

https://kb.netgear.com/24233/How-do-I-erase-the-configuration-settings-on-my-Nighthawk-router

https://kb.netgear.com/22697/How-do-I-install-my-NETGEAR-router-using-the-router-web-interface

[plemans · Accepted solution]

is smart connect enabled? 

https://kb.netgear.com/25346/What-is-Smart-Connect-and-how-do-I-enable-or-disable-it-on-my-Nighthawk...

[TERRYNYBERG]

I used the "routerlogin" on my desktop (Mac M4) to log into my router.  The options to change the 5GHz settings were greyed out, while the settings for the 2.6 band were still changeable.  I am not sure why the 5G options were not accessible using this interface as it always had been in the past.

[TERRYNYBERG]

THANKS.

Switching the smart connect option (located in the 2.6 area of the page) to OFF fixed the problem of not having access to the 5G band.  
Question: Why would the use of the Smart Connect option connect all of my devices to the 2.6 Band?  

[plemans]

Smart connect combines the 2x bands into a single ssid and lets devices roam between the 2 bands as needed. It wasn't that you "didn't have access", it just didn't show up as separate. Smart connect is a great feature but has to have some time for devices to roam between the bands. You can log into the attached devices through the GUI and see what band they're on. Devices can change throughout the day based off how much throughput or history of bandwidth they use. But they all usually start at 2.4ghz and migrate from there.