@BGrafals 

Look below the router on the sticker label, what is the country code? It should be in parenthesis near the serial number.

When you log into the router, look at the bottom of the screen. What is the firmware version, firmware build, and hardware version?

Thanks for the reply.  The sticker on the bottom of the router indicates it is a US router.

The firmware version is: 1.2.2 Build 20170912 rel.56240(5553)

Hardware version: ArcherC5400 v2.0

This morning I tried completely resetting the router.   On the Quick Setup tab I clicked the "Advanced" drop-down and still only see the options for overseas locations for the Mode setting.  I completed the setup and, once again:

* One of the 5Ghz channels is disabled.

* I am not able to connect to the router with any device that requires 2.4Ghz.  (Laptops and cell phones connect.  My HP Printer and other household items do not.)

@BGrafals 

With respect to the mode settings, you would leave that to none. Only DHCP needs to be selected.

The issue is the 5GHz not being available after setting up the router and getting the not supported region error.

Default the router again by holding the reset for 15 seconds.

Download the latest firwmare to reflash the software to see if the software was corrupted: https://static.tp-link.com/Archer%20C5400(US)_V2_170912.zip

When you download the file, extract it.

Log into the router and go to Advanced > System Tools > Hit "Browse" under "Manual Upgrade", and point to the folder you got after extracting the .zip file, and select the .bin file. Hit "Upgrade", and the router should start updating. Once that is done, try to set up the router again, ignore the Mode, and just finish the setup.

Thanks again for your quick response.  I followed the steps below including resetting the router to the factory defaults and loading the latest firmware.  Once again, I got the same type of errors.  At least one of the 5Ghz channels was not available, there was the message that 5Ghz was not allowed in my region, and I could not connect my printer. 

I think the issue is with the Quick Setup.  In troubleshooting the issue I performed the same steps again.  I reset the router using the reset button.  I connected to the router using an ethernet cable.  I upgraded the firmware.  I logged into the router.  This time, instead of using the Quick Setup option, I used the Basic and Advanced tabs to configure the wireless access manually.  Now, all three channels are available.  There is no message regarding 5Ghz not being available in my region/country.   Also notable is the Advanced tab now shows the mode where before the setting showed "Please Select" which was grayed out.  Also, the channel for the 2.4Ghz that was automatically selected is Channel 6, to which my printer can connect.  Previously, it was 99 and I could not change it.

At this point, I can only surmise the issue was with Quick Setup.  Since I have already spent hours trying different things, I did not take the time to reset the router and try the Quick Setup again to validate that was the problem.  I can only say that not using the Quick Setup option seems to have resolved the issue.

Thanks again for your help.

@BGrafals 

Great to hear the router is working now. Very odd, but this will probably help other users experiencing the same issue.