problem with displayport

Hi everyone!

I need your support, I have a problem that has come up repeatedly.

the situation is that I have some optiplex 3040 computers in my company, all connected to their monitor via displayport.

the user works without problems, the question comes when the equipment is suspended after a certain time. At the time of taking it out of sleep mode, the equipment turns on (you can hear where the fans and the hard disk enter, likewise the LED of the power button, it turns on) however, I have no video signal, the screen is black.

The temporary solution that I have found and that in some computers they work and in others they do not, is to disconnect the displayport cable from the port and reconnect it, this causes it to be detected and it sends me an image.

What could be the reason why this happens?

I appreciate your help infinitely.