I too had same problem.
to resolve the issue follow this procedure
- Hard reset the router ;
- Connect to the router with Ethernet Cable ;
- go to 192.168.1.1
- login using admin as userid and default password as admin (if you have not changed it before )
after login click on management tab
- on your left hand side there is a option called " Access Control" click on it then select user management and then you can change your UserID and Password