The monitor cant view video

Question

i made the monitor(likom hd15a) as the extension monitor as my main monitor (i'm using laptop) is damaged. The main screen stil can be viewed but the pictures change very slow(laptop screen). Ok the problem is i cant view the video in my new likom hd15a. only the video! sound appears but only dark scren seen meanwhile i can see the video move slowly in my laptop screen. thnx to anyone who solve this