dell e7470 docking station displayport issue

Hi guys,

I bought a new monitor recently and it only has HDMI/display port, so I decided to use display port on the docking station and can't get it working.

I can see dell logo when restarting laptop, as well as Windows logo, but screen just went to black/flickering when it comes to Windows logon screen.  

I don't have any issue with DVI port on the dock station and I tested this new monitor with other PC on display port no issues at all.

All dell drivers have been updated, I can't think of anything else...any suggestions? 

Thanks. 

Rocky