DP to VGA cable does not work on Dell D6000 docking station

[DimitrisB]

Dear all
Please if you can help me with that.
I have 3 Dell D6000 docking station and the DP to VGA cable not working on DP port.

I have try with:
1. DP to DP cable --> working
2. VGA yo VGA cable with adapter VGA to DP --> working

I have already try many monitors. The DP to VGA cable is working on a small PC with DP.

Updated docking drivers and firmware without results