@shahzeb 

Some things to try as they helped others:

Clear your browser history and cookies.

Try a different browser.

Try a different computer.

Try http://tplinklogin.net/ instead of 192.168.0.1 as I have had one work and the other not.

@shahzeb 

Could be the router has changed its IP Address. Easy to check, look at the IP Address of your device. If it is 192.168.0.xxx then the router is still at the same IP Address. Possible it could have moved to 192.168.1.0 though and if so, you device IP Address will show that as it would be 192.168.1.xxx

Rather than 'restarting' the router, and I'm not sure what that meant? Have you tried RESETTING the router (using the hidden reset button?)? Normally it restarts after the f/w load itself. You could have some corruption of the f/w.

" Searched for it through TP Link's website "

You shouldn't have had to do that? All you had tosearch for it, all you had to do was go to the Support page for the router and used the download center (https://www.tp-link.com/us/support/download/archer-ax20/#Firmware), hopefully you got the f/w from the same page. If not, get it from there and try again.