The problem with the video outputs of the video card

I will try to describe the problem in as much detail as possible: The monitor is connected to the video via mini Display Port - Display Port. I start the computer, it turns on, but the signal to the monitor simply does not arrive. Although yesterday everything was fine. When you press the shutdown button on the system unit, the computer turns off at the same second, that is, there is no shutdown, the power is simply cut off and the computer stalls. Next, I connect via HDMI cable, the computer turns on, the peripherals (mouse, keyboard) are detected, everything is on, it works, but the signal is still not received by the monitor. In this case, when you press the shutdown button, the computer is already shutting down correctly, the computer turns off after 10-15 seconds. But the signal is not received by Monique. It's not about the monitor, I tried to cut it to the TV set, the same problem. I sin on the outputs of the video card. Or maybe something else?