Our 20 year old son (student living at home) filed taxes before we could use him as a dependent

Our 20 year-old son filed his taxes before we did. He is a student living at home. When we used him as a dependent on our taxes, the IRS denied it because his social security number was the primary. We paid $50 for a Turbo Tax Expert to give us advice. They told us to wait 2 to 3 weeks for his Return to be processed. We waited a little over 3 weeks and were still denied. Any help would be appreciated.