Leave the wall wart for the PowerCab plugged into the 110. Pull it
out of the powercabpanel and measure the DC voltage from the inside
of the barrel to the outside. If that is zero you have some sort of
problem with the power supply - if not you need to check the rest
of the connections - everywhere, one at a time, working from the
power supply plug towards the PowerCab itself.
Unplug each 'leg' and check power as you go. Do NOT attempt to
measure the output of the powercabpanel by sticking the meter
probes into the plug - find and use the contacts on the backside of
the plug (it is far too easy to cause the feelers to misalign if you push
meter probes into it).
Look inside the PCP plug socket - where the PowerCab is plugged
into it and check if the feelers are all straight and not touching each
other and parallel to each other.
There are ways that either the PCP or the PowerCab itself can have
a broken solder joint "inside" of them. I'm not the guy to tell you if/how
to fix those your self.