Second U2415 not recognized in chain, 2012 Thinkpad T430

I have purchased two U2415 monitors.  They are hooked up to a Lenovo Thinkpad T430 with an Intel HD Graphics 4000 driver.  The two monitors are daisy chained with the DP / mini DP cable.  I want to configure to a dual monitor display, but the second monitor is not recognized and is mirroring first monitor.  DP1.2 is enabled on the first monitor, and disabled on the second monitor.  Any advice is much appreciated.