PC won't connect to monitor

Hi,
i have a problem with my newly bought pc. When i connect it via any port (hdmi, vga o.s.v) to my monitor the monitor cant find the pc and just enters sleep mode. The monitor is also new and i don't think there's a problem with it. The pc runs fine (all the fans run on the grapchis card, cpu, o.s.v + all the outer fans in the case + all lights are on) so i'm thinking the problem might be in the connection between the pc and monitor. i would really appreciate any help!
Thanks!