I figured out the problem...When the power button was switched off, the 19V power was cut to the fuse block, turning off the power to the USB Hub, but because the Pi was still powered through the MCS Board, the USB Hub was still receiving 5V through the Pi's USB 3 port. This power then back-fed through the Hub's power lead, through the Binzet DC Transformer, to the fuse block. The fuse block would then show 5V, which was being sent to the on/off +V to the MCS board, keeping the Pi alive.
I fixed it...I added a 5A Schottky Diode between the fuse block and the Binzet DC Transformer which is powering the USB Hub. This prevents voltage from backfeeding, allowing the on/off +V to the MCS Board to go to Zero, signalling the MCS App to shut the Pi down.
I fixed it...I added a 5A Schottky Diode between the fuse block and the Binzet DC Transformer which is powering the USB Hub. This prevents voltage from backfeeding, allowing the on/off +V to the MCS Board to go to Zero, signalling the MCS App to shut the Pi down.