How can I help my son succeed in life when he refuses it?

When my son was a teenager, we sent him to live with his dad because of the constant disrespectful attitude. A week after he graduated, his dad made him leave because of the same issues. All four parents tried to talk to him, and he just refuses help all around. He is now living with his grandparents. He had a job, and took steps to get his license and an insured vehicle. I thought he was heading down the right road, and then he tells me he quit his job because he didn't like it. I just don't know what to do.