@Daddy123456 

Hello, if you cannot login to the web management page of the C6, please check the below:
1. Ensure that your device has connected to the router either by an Ethernet cable or by wireless.
2. Open a web browser and enter 192.168.0.1 or tplinkwifi.net in the address bar and give it a go.
3. Otherwise, please check the default gateway of your device and use it to access the internet: https://www.tp-link.com/faq-838.html
4. Meanwhile, you can use different web browsers and devices to access.
5. Besides, you can try to reset the router and login with the default username and password.
Here is an instruction you can refer to https://www.tp-link.com/en/faq-2236.html