I have a Lennox condenser model Number 13acd-042-230-01. The contactor switch does not stay in. It pulls in, the fan runs, the compressor kicks on and then within two minutes it pops out.
I have cleaned the contactor switch with electrical contact spray and replaced the thermostat with a brand new one. That did not work.

You should have 24 volts at contactor for it to stay in, check voltage at contactor coil to see if 24 volts is present when it deenergizes.
I wonder if contactor has shorted windings drawing excessive current.
Also I would suspect low voltage wiring from air handler to compressor unit, any short may draw excessive current?