Allright, I've been banging my head all morning on this wonderful monday mystery. We have got T460s i5 6200u specced machines for our clients that typically need docks, either the Pro or Ultra's.  We have had no issues with monitor output on the docks with Windows 10 enterprise 64bit with Anniversary.

However, we are now starting to roll out our the imagages on the T460s laptops with  KMS server Enterprise Windows 10 with Creator Update.

Since then, I have not been able to get any new T460s to reliably output via VGA, Displayport or DVI through an ultra or pro dock.  With the laptop lid closed and with full power running, and just the LCD laptop screen off, the docks refused to output to any monitor.

Only when you slightly open the lid will the monitor output on the docks "wake up" finally up.  Monitor output does work if you have the laptop lid open when docking but neither are a real good solution

The lenovo update has been run and  everything is updated included dock firmware.  I've disabled sleep mode just to make this easier with docking and undocking

Yep, it sure as hell was the problem after 8 hours of pulling my remaining hair out and 1.5 with Lenovo chat support that equaled nothing.

I just rebuilt the entire OS with Anniversary 1607 build of Win10 Enterprise and no creator update on the same laptop and now external monitors when docking now works properly, both with power on and coming off from sleep mode when docking and undocking.  So those of you with sudden dock issues with monitor output with Thinkpad serious, get rid of Creator update and go back to Anniversary Update 1607 Windows 10 builds.

So Lenovo, you seriously need to look into and update your Intel HD drivers and possibly dock firmware for the Win 10 creator update for the Thinkpads

I checked T460s with Win10 CU and could not reproduce a problem:

1.  with the system undocked, close the lid

2.  the system goes to sleep

3.  put the system on the dock (leaving the lid closed), then press the power button on the dock to wake it up

4.  the output is displayed on the DP monitor that is connected to the dock

Am I doing something differently than you?  What else should I try here?

Figures I'm the only one with with a problem.  Most of my clients don't have their laptops go to sleep, they hot dock with laptop on and thats were the big problem was, in that the dock woudlnt output any video on display port or DVI or VGA no matter what when the laptop was on. Only by opening the lid and closing it will the dock output the video.

When I tried docking in sleep mode with the T460s and waking it up, the resolution came out incorrect on the 1200p monitor, it was 1080p, same as the laptops resolution. Again, only way to fix it was to open and close the lid.

Also keep in mind I'm not running Lenovo Windows image, I wipe the machine and install our Windows 10 enterprise with bit locker encryption per goverment requirements, so there is that variable

What are you setting as lid close action?  Do nothing?

I would like to keep testing to reproduce the problem, but I need you to give me some clues  :-)

Yes, lid setting is set as "Do Nothing" in the power settings of Windows 10. What other info would you like? Also, it was not a patched Windows 10 with Creators Upadate, the laptop was imaged with an updated ISO with creator update included. Dunno if that matters but that is one variable. I also have hibernate disabled entirely as it causes more problems then its worth in my experience. 

I re-tested with lid close action set as "Do Nothing" and now I see the behavior you are reporting.  When I dock the system with the lid closed, the system stays powered on but the DP monitor stays in sleep mode.  Until I open the lid and then close it again.

Workaround:

With the system on the dock, lid closed, and no output to the DP monitor:  Press WinKey+P, then press down arrow 3 times and enter.  

As for root cause, I have no idea.  For some reason, Win10 1703 does not "see" the monitor in this case, even though Win10 1607 did.  So it stays in "PC screen only" mode.  Win10 1703 needs to be manually set to "Second screen only" mode (what my workaround does) and only then does it "see" the monitor.  I need to investigate this more and probably ask for help from a video guy.

Awesome! Well... not awesome in the problem of itself but now you see the problem lol!  And yeah...there is no way I can tell clients to do that keyboard shortcut, never gonna happen lol.  

Did you happen to see the incorrect monitor resolution oddity waking up the laptop on the dock from sleep mode? Again, our external monitors are 1200p Asus and when I do sleep mode wakeup on the dock, the resolution is stuck at the laptops LCD res of 1080p until you flip the lid 

In the meantime, I will have to stick with Anniversary 1607 ISO builds on the T460's until  the Creators Update  "oddity" is hopefully fixed at some point. 

I saw wrong resolution on the monitor when the projector setting was "duplicate", then the monitor resolution was same as internal LCD.  when it's "second screen only", the monitor resolution is correct.  Is it the same behavior you saw?

I think CU is picking random/wrong projector settings that are not lining up with what the user is actually trying to do.

You mean when you had the laptop powered off and the lid closed when you docked and powered it on? Thats when the incorrect monitor resolution occurs and only opening the lid corrects the resolution