So here is the story, Im dumb and I uninstalled the nvidia graphic driver and the nvidia geforce experience ( because of a problem on a game ) and after the restart, no signal... I rebooted the PC 100times, changed my HDMI cable... I faced this issue a long time ago ( for the same reason ) but after a few reboot, it suddently worked!!!( by the way I didnt uninstalled the nvidia geforce ecperience that time )
I am on my laptop right now to type this message and I tried the monitor on the laptop and it worked so I think the problem come from my computer.
My computer is an Alienware X51
A help could be really helpful!!!