Freeplay Zero will no longer power up

[horus]

Not sure what's going on.  When I hold the power switch the Freeplay Zero won't boot up.  The batteries are charged, and it will boot up and operate if i plug a micro usb cable directly into the Pi.  I've opened it up and the power switch on the Freeplay board is still within the grasp of the switch cover.  There's nothing visible inside or out that would indicate any damage.  

I built it about 3 weeks ago and have had no problems until now.

Any suggestions?