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Hello and welcome to just answer. First make sure that all of the evaporative emission hoses and lines are ok and were not damaged during the collision. Make sure the gas cap is ok. Then make sure that there is over 1/4 tank of fuel and just drive the car for a couple of days. Once the PCM (engine computer) runs it's self test on the EVAP system, then the monitor will pass and you should be able to pass the test. It sometimes takers a couple of days, so be patient.
I hope this helps, and let me know if you need further assistance with this.