@ihsankhan 

If you can't login to your TP-Link router on the Tether, please follow the guide below to troubleshoot:

What if Tether failed to log in my TP-Link product?

If still cannot login, please show us the login failed error message, which may give us some clue.

You can also try to power off then on the router, as well as login out the TP-Link account on the phone then login again to confirm.