its a pressure switch on the oil pump, if the oil change is actually related to it not starting, the oil pressure sensor would be why.
if you unplug and/or jump the sensor, it will start if that is the issue. dont leave it hanging while running too long, and also dont drive it / run it long, as you might actually have low oil pressure and not a bad sensor, just see if it starts.
After either solving or eliminating that, the diagnosis can point elsewhere.
i would also check for fuel and spark.