My snapper wide area walk behind mower [ commercial 48 inch 14 hp kohler] will not move in forward gears it seems to shift into all 5 gears but will not move, reverse works fine. I replaced the drive belt and checked the key on the pulley, it is fine. I don't know what to do next.

Hi,
Need a model number; went looking, but there are quite a collection of model variations. Snapper is now owned by Briggs, who owns many other manufacturers as well. Many other people made mowers for Snapper before and after Briggs became the owner.
Peace,
Clarke