Clutch question

I'm not sure who to talk to and your office is closed now but here is the situation. Last week we installed a dual disc clutch in a 2010 dodge. Everything went fine and we test drove it, it shifted smoothly with no problems. The customer picked it up and they drove it around with no problems, I think they said they put around 2-300 miles on it. Well today the customer was driving it and she put it in gear and let out the clutch and nothing happened. It didn't take off and then just shortly after (2-4 seconds) it just took off. I asked her if there was any grinding or weird noises and she said no. It sounds to me like the clutch didn't engage or something. Anyone know what is going on?

Maybe the throw out bearing hung in the fingers or the fork got stuck some how

I would pull the slave out and check the fork movement, see if it moves freely. The only way you would get a delayed engagement would be if something is hanging up.