PIC32 only works when shorted to ground
I agree with Erik that there could be an issue with the hand assembly of the second board. If the first and second boards are exactly the same design, but one works and the other does not, then it's a component or assembly or freak damage/accident issue. 

I have had a recent experience with hand loading 20 small bat tracking boards I designed, which each have small power circuits, memory, gps, and a microcontroller (Atmel ATMEGA328P). of the 20 boards, 16 worked immediately after assembly, but 4 were unresponsive to programming. I could not work out exactly what was wrong, as all solder joints were fine after inspection with microscope, but after SMD re-work replacing the MCU ICs with some spare ones, (TQPF-32 packages, easy stuff) they immediately worked.

I suggest after you try flux + re-heat each solder joint to see if it's a bad join and therefore bad grounding issue, you should attempt to replace the microcontroller IC. Make sure you establish that it is not a solder short circuit or other external fault before doing this! You may just fry/permanently damage another one if you immediately replace before elimination of other options.