sounds to me like you are trying to connect by wifi instead of ethernet.
I'm an IT guy and this's the first time for me to ask for help because I've tried many things to fix this issue and failed.
I'll tell you what's the full case here so it would be more convenient for you to assist me.
I have one internet router (Huawei HG8245T).
Its wireless signal is kinda weak so it can't cover all of our house, so I bought (Linksys WRT 1200AC) Wireless Access Point.
I made a network cable (30 meters) 3M Sheilded.
I connected my PC with the cable to the HUAWEI Router first to make sure I've fixed the cable properly, it showed me the connection is up and the speed is 1Gbps (Yaaaay)
but after like 2 minutes I didn't get an IP from the router, it gave me an APIPA....
First thing I did is to setup my IP to Manual with the same IP Range and of course I setup the gateway to be the router, it worked and I can PING the router, I can even access the router's settings page on the browser, but I can't access the internet and it shows me (CONNECTED BUT NO INTERNET)
I've tried with another PC and same problem.
I've tried to setup the Linksys AP and same problem.