Won't power on using the power button on the back of the unit

Hello,

I just picked up a Macintosh IIx that was being sold as recapped and working, but when I got it home to turn it on, it showed no signs of life. Nothing out of the power supply, and pressing the power button on the back of the unit did absolutely nothing. After some research, it was found that the power supply could be turned on by applying three volts to Pin 15, and doing so worked. The machine turned on without a problem, and made the startup chime. I checked both PRAM batteries, and they seemed to be fine. I also tried applying three volts from my bench power supply to the battery holders, but pressing the power button still did nothing. However, the power button does work for turning off the machine once it has already been started. I was wondering what could be going wrong, and how the issue can be fixed.

Thanks!