Do you have both cameras connected via Etherent or USB? Is it consistent which camera fails to connect?
You can see the IP on the network settings screen, you might try pinging them both to check connectivity. You can also set a static IP address on that screen.
It is possible that the operating system on one of the cameras is corrupted in such a way that the webserver that serves the control web page doesn't work. If it's always one camera that fails, you may try reflashing the OS SD card and see if that helps.