I have found the onscreen keyboard doesn't open up all the time when there isn't a keyboard present, like it should (IMO anyway).

Here's how I get around it until Dell gets a chance to diagnose and fix the issue (*coughhintcough*)

From the lock screen:  On the bottom-left corner, click on the "East of Access" button and choose "On-Screen Keyboard" to login.

From the Start Menu: Swipe to Apps, swipe right to "Windows East of Access" category and select "On-Screen Keyboard"

Not optimal, but it works for me...

I have a Venue11 pro and the same issue at random times.  I was able to correct it (for the moment, at least) by performing a hard reset - hold in power, swipe down when prompted, wait, then reboot and the keyboard reappeared normally.  This is just one of several significant problems that have convinced me not to get any more of them.  The latest is that it has stopped charging while on the dock! On hold for ProSupport now (10 minutes+)   Disappointing, maybe next generation will be better.

I use the same tactic, but figure once back into the OS you should be able to re-enable the base functionality.

I have looked around but can't find any settings to enable or disable this

Same problem here.  And it should be noted that this is WITHOUT the travel keyboard attached.  I know that either Dell or MS have preprogrammed the system to disallow the on-sceeen keyboard IF a physical KB is detected (says so in  the travel keyboard "features").  What I've found is that if the auto-KB doesn't come up at the logon screen, its not going to work as expected.  Oh sure, I can bring up the Ease Of Access keyboard, but forget auto-KB action during that session.  REBOOT!!  After reboot, the auto-KB usually comes up and works flawlessly.  But that's a terrible solution and annpying when I just started the system from OFF without a keyboard within 50 feet!!

My bet is that this is NOT a hardware issue, but rather an inconsistency between a Dell driver and the Windows 8.1-pro 64bit OS.  I never have this issue on my Latitude-10 ST2 tablet (which is always very refeeshing actually) running 32bit Pro-8.0.  

I've owned all 3 of Dell's windows tablets (7,8,8.1), and my Venue rocks- except for this issue.

I believe that the system is erroneously detecting (for whatever reason) a physical KB from the magnetic contacts on the bottom. At which point it kills the On-Screen KB. Dell meeds to either rewrite or disable the "disable OSK when physical KB detected"

I'm glad Im not the only one woth this issue.

-OEM