[NAME]  If the display's resolution is 1920x1200 or lower, try using a DVI to HDMI adapter instead, which is a simpler setup.  DisplayPort to HDMI requires an actual signal conversion since DisplayPort and HDMI aren't just differently shaped connectors but completely different signal types.  DVI and HDMI up to 1920x1200 are identical signals at an electrical level.If your display's resolution is greater than 1920x1200, then a typical passive DisplayPort to HDMI adapter won't work, but an active adapter probably would, and it might even work around this problem with lower resolution displays if the DVI to HDMI option doesn't work.  Passive DP to HDMI adapters rely on the source system supporting "Dual Mode DisplayPort", which allows the source to switch to native HDMI signaling rather than DisplayPort.  But it's fairly common for the maximum resolution in HDMI signaling mode to be lower than when using native DisplayPort, partly because the HDMI spec has always lagged behind the contemporary DisplayPort spec. And I'm 95% certain that the HDMI spec supported by that dock's DP outputs limits resolution to 1920x1200 in HDMI mode.  By comparison, an active adapter allows the source to continue using DisplayPort signaling, thus allowing higher resolutions, because a chip within the adapter performs the conversion to HDMI, and newer adapters would support newer revisions of HDMI that can support outputting higher resolutions in HDMI mode.Also, does disconnecting the VGA display make a difference?  Depending on the resolution(s) of the display(s) you're trying to run, which you didn't specify, you might not have enough bandwidth from the system be able to run your particular combination of displays.  Another factor there is whether you have a first or second generation dock.  Unfortunately Dell used the PR03X code across both generations and even between the E-Port and E-Port Plus variants, the latter of which have dual DisplayPort outputs.  The reason THAT can matter is that the first generation docks only operate in DisplayPort 1.1a mode, whereas the second generation supports DisplayPort 1.2, which supports much higher bandwidth both from the system and out from the DisplayPort output.If none of that works, do you possibly have a display with an actual DisplayPort input you can test just to verify that the DisplayPort output is working at all, without relying on an HDMI conversion by the dock or an active adapter?
Hello everyone.  I have E7470 docked on PR03X and I need to connect my HDMI monitor via DP in PR03X, but it's not detected by my system (W10x64). I don't have this issue with VGA/DSUB and integrated HDMI in E7470, but somehow my laptop cannot recognize my monitor when I'm trying to use external DP. I have two different cables and even I bought new more powerful AC adapter, 130W model PA-4E, recommended for this dock station.  Can you help me? I keep my drivers updated, but maybe somehow I missed something, or anything else I messed up. 
DisplayPort doesn't work on PR03X with E7470