As in hardcore mode the number of slots is limited to 8, when you enable it with more than 8 slots set on the server, any player that joins after the first 8 cannot join. You should make it open more slots, maybe open one rifleman, breacher or advisor slot per extra player joined, or one rifleman, then one advisor, then one breacher, so classes doesnt get abused from start but allows more players to get in 🙂