Unexplained moisture over a "crawl space" - help!

Hello! We are getting some moisture/condensation/water under our kitchen floor. We noticed because it is causing mold and rot in certain areas. No obvious leaks so suspect condensation trapped between the layers of flooring. A portion of our floor is over an unconditioned space. We are wondering if sealing or insulating could help. The space is not accessible without tearing things up. We're not sure who to call to get it fixed. Has anyone ever encountered this issue? It's a long shot, but we figured we can't be the only house in the area to have this issue! Thanks. Amy