Internet service can fail for a number of reasons. The service provider can drop their connection, or a computer's network card can fail. One of the reasons for Internet failure is a malfunctioning network jack. Business and homes sometimes have ethernet network systems built into the walls of their buildings. Occasionally these network jacks can burn out or become lose. It can be troublesome to replace these jacks so it's important to test the jack before attempting to replace.
Test the jack for a signal. Insert an ethernet loopback jack or sniffter into the jack. It will detect the Internet connection and give you a proper display light if the jack is working. This is the easiest way to check whether an ethernet jack is working.
Use your laptop to detect the ethernet signal from the Internet jack. Plug your laptop into the wall jack using an ethernet cable. Bring up the Network control panel on a Macintosh or the Local Area Connection network control panel on a PC. The computer will display an IP address and a subnet if the jack is working, such as 220.127.116.11 / 255.255.255.0. If the jack isn't working it will display a self-assigned IP address such as 169.X.X.X or the control panel will say 'network connection not found.'
Replace the ethernet cable with another cable. Try the test again, and see if the results are the same with a different ethernet cable. If the connection fails, you will likely need to have the jack replaced. Contact your building's Internet administrator and request service for the Internet jack.