Issues

My friend and I, with whom I've flown in the NGX with DP many successful times, sat down the other day to do a flight from Memphis to Midway. He connected to my multiplayer and then my desk pilot, and we set it up just as we had when it had worked. But, when I flipped switches on my side, he couldn't see them be flipped. However, when he flipped switches on his side, I could see them be flipped on my screen. Why is this? Thanks in advance.