Can't connect to PrintrBot

Last Saturday I couldn't connect to the Printrbot from my computer. I thought maybe it was the cord, so I found a couple more of the same cables and tried them, but none of them worked. And it kept sending an error message through pronterface (by the way pronterface is the program I use to print to the PrintrBot). The next day my brother Nicholas came over, and he told me that I probably need to restart the controller board. But he hasn't done that on that 3D printer so I will have to google it, I am pretty sure I will need to connect to the board to send a restart command, but I can't do that because that is the reason why I have to restart it. So, for now, it is just sitting on my desk till I can get it fixed.