Precision 7710 (2016 build) won't turn on - flashing battery LEDs

Issue: 7710 (2016 build) won't enter BIOS startup.  Using the Dell powerbrick, the battery Led is constant white or blank.  When power key is depressed, Power on LED turns white for a second or two, then blank, then the battery LED flashes  2x Amber: 4x White: 2x Amber, 4x White, and repeats.   What does this error code mean? 

I have an identical setup (bought as a set), and have swapped the battery between the two, and used the same Powerbrick Powerbrick and both batteries work fine on the working unit. 
Neither battery nor powerbrick works on the non-working unit.