Probably positive output is connected to GND or something else on the back connections.
on mine
a3 a4 and a5 are connected
a6 a7 and a8 are connected
a9 -s and - are connected
+ +s and a10 are connected
Picture of back attached
it looks like ground is supposed to be attached to + +s and a10 though since i don't understand the back of the power supply nor did i know it existed i wont try it till some one can confirm my suspicion or give a different idea on how to fix it i tryed it simply maxs the voltmeter built into it