What does the red X mean? - DirecTV DVR

For DirecTV TV services which include DVRs and receivers, What does the red X mean? I tried to turn my tv and box on, but the cable box won't turn on. Once I finally got it to do anything it just made a red x on the tv screen. I restarted everything and unplugged it all, which it worked for about an hour. But Now it keeps shutting off and not working at all.