DisplayPort not recognized

[MR ZenWiz]

I just bought a refurb HP 8740w "EliteBook" and installed my Xubuntu
16.04 drive in it.  Everything seems to work so far except the display
port.

To verify that it works, I just took out my Linux disk and put the
Win7 disk back in, and it has no trouble recognizing the DP connected
TV.

In Linux, I get nothing.  The Display app is set to configure new
devices when they are connected, but nothing shows up.  The monitor
control app that lets me decide where to place the screen does not
show up.  There are no errors I can see about this in the system logs
or the Xorg log.  Even xrandr does not list the extension monitor.

What next?

Thanks.
MR