D-Link 5ghz band not detected by devices

[Japhasca]

I have a D-Link Dual Band Router, a bit old, it's a DIR-825 hardware version B1. About a week ago my Switch and my Samsung Note 5 stopped being able to pick up the 5ghz band. The 2.4 works fine, and the lights on the front of the device appear to show that both are still broadcasting.
I'm not even sure where to start since I set this up so long ago, in fact all I really remember was being on the phone with WoW Cable tech support for an hour since their cable modems wouldn't let me use my own wireless router without some remote shenanigans, including guessing at the MAC address. It was an ordeal I'm not really looking to repeat.
Any ideas? Is it something I can fix? Or is it just dying and needs replacing?

 

[RealBeast]

I have a D-Link Dual Band Router, a bit old, it's a DIR-825 hardware version B1. About a week ago my Switch and my Samsung Note 5 stopped being able to pick up the 5ghz band. The 2.4 works fine, and the lights on the front of the device appear to show that both are still broadcasting.
I'm not even sure where to start since I set this up so long ago, in fact all I really remember was being on the phone with WoW Cable tech support for an hour since their cable modems wouldn't let me use my own wireless router without some remote shenanigans, including guessing at the MAC address. It was an ordeal I'm not really looking to repeat.
Any ideas? Is it something I can fix? Or is it just dying and needs replacing?

I would download a cellphone wifi analyzer app (many free ones available for iPhone or Android) and use it to determine if there is a 5GHz signal. I suspect that the 5GHz radio has malfunctioned, but have no idea if you could repair -- if no signal it's probably time to replace.

 

[bill001g]

Use your phone and get one of the free network scanners apps. They are really should not show anything different than the built in network list but they are easier to use.

Most have graphs showing the signal levels and the names of all the routers it sees around you.

Unfortunately that is exactly what a failed radio in the router looks like. The router has it enabled so it turns the light on but it does not mean the radio chip is actually able to transmit. It is a fairly rare thing to happen.

Before you replace the router try a factory reset with the button on the back. You will have to completely reconfigure the device but maybe you get lucky