Hi Ken,
I'll assume you are using Windows OS. Please take a look at the bottom right corner of the screen, there should be an icon of displaying something like a monitor with the tip of the LAN cable next to it. Right click it and from the drop down menu choose "Open Network and Sharing Center". Once there click the blue link in the left part of the window which says "Change Adapter Settings". In that window select your Eternet adapter, right click it and choose properties. There you will see this little window:
If your IP is not configured to be obtained automatically that could cause problems with LAN connection. Likewise, if your connection requires custom parameters provided by your provider, enter them in the appropriate fields. Let me know if this helps. If not there are still some things you can check out, but do this first.