@imran02 

After you login the router via Tether App, did you bind the router to your TP-Link ID as well? If not, you will still need to use local password of the router to login the web interface instead of the TP-Link ID and password.

If you are not sure whether your router is bound to the TP-Link ID, please go to Tools->TP-Link ID page on the Tether App to have a check, or please send me a private messgae to provide the MAC address of your Archer C60 router.

  @imran02 

Hi, upon checking the MAC address, the router is not bound to any TP-Link ID, when you try to bind it again, please add the owner account first instead of manager account.

If you fail to add owner account as well, please try reset the router to factory default settings, then try to bind it again.