@BillF 

You can reset your router to factory specs which will allow you to set the user id/password and to ensure everything is back to what it should be. If you suspect a security breech, do change all of the passwords including the WIFI passwords. If the router has the settings, I prefer to set it so all changes must be made with a connected PC and not over the internet.

@ArcherC8 this would not be the first time I have reset to factory default in order to regain access to the lost local password.  Is there a way to determine if the device was compromised remotely?

I would rather not have to reset the device every month 'just in case'.

How do I know some hacker has not gained access to it?  I seem to have a lot of bandwidth problems that are difficult to identify. 

@BillF 

When you bind your router to the TP-Link Cloud the router will start using the TP-Link ID and password as the login. If the internet was cut out, the same TP-Link login credentials will still work and allow you to log in.

If you have a concern about remotely logging into the device, make sure DDNS is disabled (Advanced > Network > Dynamic DDNS). By default, it is not enabled, but if you do, disable or unbind the service. In that case, you can only log into the router while on the same local network so either connected via Wi-Fi or hardwired to the router.

Some login screens will allow you to login with the local credentials, but if you do not see that option unbind the TP-Link Cloud service, and the router will revert to the admin username login where you can change the password by going to Advanced > System Tools > System Parameters.

@Tony that is odd.  When I linked it, restarted it, the local password worked.  A week later it was working.  A month later?  It doesn't.  Is there some kind of timer?