Sometimes 2 things can occur that is Arduino related:
There is a lack of contact due to number of connection pins. One thing you can do is to removing the SpikerShield and carefully reattaching it again to the Arduino board.
Arduino can mess up the internal firmware and needs to be flashed again, this is easy to spot, the last RED LED(LED 6) blink or keep always on if this is the case.
Then you would need to follow the set of instructions explained in FAQ>How to reupload the Arduino code