Fired due to background check

I just lost my job because of a background check. I have a 4th degree theft felony from 3 years ago I didn't serve jail time. I did three rounds of interviews and the topic of criminal record was never brought up. I filled out a background check form before starting and again it was never brought up. Now a month after starting they are saying they have to terminate my employment due to my felony. I'm pretty discouraged right now I've been trying to turn my life around since I was charged but it seems like no one will give me a chance.