@lavokuxo 

Hi, 

May I know who is your ISP? Is it a cable modem or DSL modem? What if you connect your modem directly into your computer, will the internet work?

If yes, with the cable modem connected to the blue/WAN port of C1200, please follow the below instruction:
1. Unplug the modem’s power cord and unscrew the coaxial cable
2. Connect the modem to the router’s WAN port and make sure the router is powered on
3. Plug the power cord for the modem back in, but leave the coaxial cable disconnected
4. Wait 3-5 minutes and reconnect the coaxial cable
5. Wait for the modem to reconnect and then check for IP and service

While if it is green, please log into the web page to check whether it obtains the IP address from the modem.
Note: You can go to Advanced-status page to check it; how to login: https://www.tp-link.com/us/faq-712.html

If it still doesn't work, please connect your computer to the cable modem directly and check its IP address, default gateway, and DNS.
Note: How to find them: https://www.tp-link.com/us/faq-838.html please show us a screenshot of the status-details page.

Then please reconnect to the C1200 by WIRED CABLE and login to the web page; Go to Advanced-Network-Internet page to clone the mac address.
Note: Please clone the computer's mac address.

Any updates, please keep me posted.