IMHO, the sealer would be a waste of time and money. To be sure you can do the moisture test. Tape a 3' x 3' sheet of plastic to the floor. Check it in a few days. If there's moisture between the palstic and floor, you have a moisture problem. S sealer may or may not be the solution.
If its dry, you don't need a sealer.
Perhaps the pros on the board will have a different opinion.