plugged and unplugged monitor

[<michaelmorgan937@gmail.com>]

I have a linux machine for scientific calculations with GPU installed. It also installed GUI but normally the default start mode is just terminal (multi-user.target).

 

If I start up the machine with a monitor plugged into the GPU (HDMI or Displayport), the monitor works well (showing the terminal). However, if I unplug the
HDMI cable and connect it back again, there will be no signal to the monitor any more. The same thing happens if I start up the machine without a monitor. I
can ssh to the machine, but there is no signal if I plug in the monitor.

 

What could be the problem?

 

Thank you very much.

 

Michael