The PC2X does not use the KFP2S pedal.

The KFP2S is a Double "Piano Style" Footswitch  - it has two pedals
with a single stereo connector plug. This is used with the Kurzweil
SP series and Troubadór only.

The KFP-2M is a Double "Piano Style" Footswitch with 2 mono plugs  -
it will work with the PC2. Make sure the appropriate plug is
connected to Switch 1 and 2 input. Perhaps the customer reversed
them, and the pedal on the left is connected to Switch 1 (sustain).

The PC2 expects to see mono connectors at the inputs for switch
pedals. With the PC2, you can use the following switch pedals:

FS-1     Footswitch Pedal

KFP-1     Single "Piano Style" Footswitch

KFP-2M      Double "Piano Style" Footswitch with 2 mono plugs

And of course,

CC-1      Continuous Control Pedal

The PC1X has only 1 dual switch pedal input - it needs the The KFP2S
(two pedals with a single stereo connector). you can also use a FS-1
KFP-1, but you will only get sustain (cc 64). One could use the
KFP-2M, but again, since it has two mono plugs, only the pedal that
is connected would work, and it would be sustain.