hi! if i connect a monitor directly to the displayport of the x220, the monitor realised the computer put doesn't display anything. if i do so with the vga-por

hi! if i connect a monitor directly to the displayport of the x220, the monitor realised the computer put doesn't display anything. if i do so with the vga-port all works fine! did you ever connect a monitor to the displayport a get it work? if so, can you give me some help? thanks alot! lg oxyl