Issue with O Ring
If your WaterPlant CO2 system will not puncture the CO2 cartridge. The issue may not be the pin being too short, but the O ring being too LONG.
1. Remove the O ring.
2. Use razor blade to cut 1/16 of an inch off the side of the O ring that goes over the pin.
3. Put the O ring with the cut side facing into the housing, so the cartridge is on the uncut side.
4. The pin should now be able to pierce the CO2 cartridge.
Hope that helps,