Sony Monitor Speakers Are not working!

Hello,
Recently a computer tech came and moved my computer to a different room therefore had to unplug and replug everything. He also rebutted my computer, and now my speakers which are inbuilt in my monitor is not workingg. I am ceratin that it is not muted, and my soundcard is working because my headphones work.
So how do i connect my speakers and make them work !?!? :(
please help, its annoying not being able to listen to musicc, or watch utube vids without sound, its not the samee -.-