Hi FurryNutz,
Thanks again for your responses.
I have performed a hardware reset on the device and used firefox to run through the installation process afresh. The automatic configuration went without a hitch, the router was able to detect my modem, the internet signal coming from the modem, and configure itself automatically. I left all the default settings including the SSID and passwords as they were.
From my ipad, I was able to log into the 2.4GHz using the default password - but not able to log into the 5GHz using the default password.It would request for the password repeatedly.
I then went into the network settings and changed the 5GHz security mode to "none", I was still not able to log into it using my ipad. The ipad would say "unable to join network". I tried logging in from my other devices and got the same error message on 5GHz.
Sidenote:
I didn't engage bridge mode in this instance since it seems the default modes are not resolved. Also, I dug up my notes from when I first configured the system (in 2013) and was having trouble. Back then, the entire internet connection was spotty on both channels. One hunch I pursued was bridge-mode. After much back and forth with my ISP, they discovered that a newly installed fibre network cable was sloppily installed a few electric poles away. When they fixed that, the internet was reliable. I then did a hardware reset and, besides changing the SSID and passwords, left everything at default (no bridge mode). Both channels have worked reliably until a few nights ago.
/Sidenote:
It doesn't seem to me a matter of wifi signals interfering, the reason I say this is that no matter what channel I try, the 5GHz signal is strong and detectable in all locations in my house. The number of strong wifi signals available in the neighbourhood has also been just as populous as it is now.
At the moment, I'm working right beside the router. What I suspect is happening is some sort of communication error between the devices ie they are not able to establish a connection. Of course, I could be totally wrong.
Any insight is most appreciated. Thanks again.