Your commissioner has full control of your league, and it's easy to miss a setting or two. One of the common questions we get is about why a team may not be able to drop players.
Allow Moves Pre-Draft - If your commish has this option disabled, no drops will allowed. You won't see a drop button at all.
Lock Free Agent and Waiver Moves - This option will need to be disabled as it will also prevent teams from making any moves.
Can I allow only drops?
In some cases, you may want to prevent players from being added, but still allow drops.
The way to do this would be to enable the Custom Daily Waivers and set each individual day to Locked.