My guess is that, never having overhauled a hub before, that you made the most common mistake: too much grease. In this case, it is being forced into the freehub body from the drive side and "floating" the pawls. The only cure is to disassemble everything, remove the freehub body, remove the seal from the back of it, and flush it out. Relube it with a light oil and repack the hub using grease more sparingly.

May the force be with you!