The upstairs has its own wireless system to extend the network from downstairs. It wasn't obvious where the problem was, so I started with something simple. I tested the ethernet cable with a tester.

Note: Making ethernet cables is not difficult and saves time, money, and allows the cable to be the length that is actually needed. You need to test them to make sure they work. So it turns out that the cable going to the modem failed. Crap. The cable is pulled through walls and tight spots. I tried putting on a new connector and it solved the problem! Upstairs wireless network now working.