Condensation - Ventilation

I have a 3/12 pitch on my house and had alot of issues with moss on asphalt 3 tab. So I had a contractor tear off everything, replace some needed places where the plywood was damaged, and put on a new metal roof. He put the metal on directly over 30 lb. felt and finished the project with a vent across the top. Now, 10 years later, my roof has become soft and is leaking condensation through my vaulted ceiling. Since I have no attic, I do not know if this is getting adequate ventilation. The contractor said it was a 50 year roof, he just didn't say he wouldn't be here to back it up for the 50 years. can the sheets of metal be taken off, reused, and some type of adequate venting be installed? What would you suggest? THANK YOU