I tried both the new LAN addresss and http://tplinkwifi.net and I can get to the router fine. The rounters user id and password screen appears.  The problem is I cannot log into it using the same userid and password I just used sucessfully before I changed the LAN address.   There is no message such as wrong password or user id.  The router shows the user id and password screen with the info I typed in.  I looked at ipconfig and it shows that I get a new ip address on my laptop and the gateway is the routers new ip address.  Internet connection works but I cannot log into the router.

Kitty wrote

I tried both the new LAN addresss and http://tplinkwifi.net and I can get to the router fine. .  The problem is I cannot log into it using the same userid and password I just used sucessfully before I changed the LAN address.   There is no message such as wrong password or user id.  The router shows the user id and password screen with the info I typed in.  I looked at ipconfig and it shows that I get a new ip address on my laptop and the gateway is the routers new ip address.  Internet connection works but I cannot log into the router.

@Kitty

Two suggestions:

1. Try a different browser... problem could be browser related.
2. "The rounters user id and password screen appears", which means it is pre-filled in by either your browser or password manages. It could be corrupt (the p/w) as that does usually show in clear text but there is an 'eye icon' possibly (I have an A20 which is similar) that you can press to see the p/w though. What I'd do is delete the p/w and type it in manually and see if it works. By the way, I uses RoboForm as my p/w manager and on the A20 it can't handle the GUI login page. I had to manually edit the data and I still have to manually press LOGIN... so the one you have could be the same problem?

Thank  you for the ideas.   I am not using a password manager or saving the password. The user id and password screen appears empty.  I enter my user id and password I had used succesfully before changing the LAN address.  When I click the "Log In" button the user id and password are not blanked out and remain what I typed into the blank form.    Nothing happens when I click the "Log In" button.  I will check another browser when I can get everyone to log out today.  But I can log in and out just fine before changing the LAN address using this browser. 
 

Kitty wrote

I will check another browser when I can get everyone to log out today.
 

@Kitty 

Don't understand? No one has to log out or why you think they have to? You can try another browser even on the PC/Device that failed without needing to do anything else?

On my Archer A20 if I have another device logged into the GUI, I get a popup telling me another one is logged in, do I want to continue and knock off the other. Are you saying you are seeing this then? Another user is logged in?

Do you also mean you can log in on another device, just not this one?

@Kitty 

What is the IP and subnet that you change the router to?

What is the IP of one of the computers (IP/Subnet Mask/Gateway)?

For one of the computer change the IPV4 information to DHCP and connect to the router compare the IP information to another computer to see what is different, but try and log in.

I meant log out for the day in that when I take the rounter down, people  do not loose  the work they were doing outside of the local LAN.  Taking the internet down is an inconvenience in our office.   I did setup the router using microsoft edge  and that worked.  Thank you alll for the suggestion.   I loaded up chrome and cleared the cashe and when I tried to login with chrome after the LAN ip change, I did get the message "broswer not supported".     I am surprised by that but I wil get over it. 

I ran into this same problem on GNU/Linux boxen, Firefox and a new TP-Link C4000...

In my particular setup, I have a second, older Linksys router acting as a switcher, which I used to be able to access with 192.168.1.2. Once I added the C4000, which defaults to 192.168.0.1, I could not access the Linksys again, like I did with the previous primary router. So, the idea was to change the C4000 to 192.168.1.1 to see if that would allow access.

As soon as I changed the Advanced->Network->LAN->IP Address from 192.168.0.1 to 192.168.1.1, the C4000 would put up a pop-up saying that the router will switch over to the new LAN address... but it doesn't. The web browser shows the web address being tplinkwifi.net and it isn't able to go there. Subsequent tries to go to 192.168.1.1 doesn't work either, nor does 192.168.0.1.

Clearing the browser caches didn't work.

The trick was rebooting the computer.

Once the computer was back up, 192.168.1.1 worked to access the C4000. DHCP Server->IP Address Pool had been automatically changed to 192.168.1.100 - 192.168.1.199. Default Gateway was filled in with 192.168.1.1. (I was going to change those next, but changing the LAN->IP Address did it already.)

I'm thinking that maybe with the DHCP address change to the computer, i.e. 192.168.0.x to 192.168.1.x, the computer lost the ability to talk to the C4000.

After this, I was able to access the Linksys with 192.168.1.2 as well, which solves my original problem.

Additional info...

Hardware Version: Archer C4000 v3.0

Firmware Version: 1.0.3 Build 20191026 rel.13901(5553)

I now know why I was having the original problem with accessing the older Linksys router at 192.168.1.2. The Subnet Mask is 255.255.255.0, which meant the default setting of 192.168.0.1 for the C4000 locked in 192.168.0, the first three components of an address. Once the C4000 was configured for 192.168.1.1, the address range was automatically changed to allow 192.168.1.x.

I think it's still necessary to reboot the computer to allow the browser to access the new C4000 address, as described in the previous post. This post was only to explain why I couldn't access the Linksys.