I would first test the line by plugging in another computer through the wired connection. (Be sure to have a known "good" CAT-5/6 cable for swapping in.) If it doesn't connect to one of the wired ports on the router, most have a couple more that may be worth trying. It may tell you whether the problem is with the router itself, a cable, or the ethernet card on the computer.

It's generally a simple task to narrow down the specifics of this type of issue by swapping in known good replacements..

Hope this helps.