Most likely the disposer port has a plastic Knock Out plug that is still in place. You can verify it by looking or with the power cord un plugged, feeling inside the disposer.
To knock it out, you will want to unmount the disposer and lay it on the floor. Use a large flathead screw driver and a hammer inserted into the drain port. Place the tip of the screwdriver against the plug and smack the screwdriver with the hammer knocking out the plug. Make sure that the entire plug was removed and remove the plug from inside of the disposer housing.
Reinstall the disposer and create a High Loop with the hose so that the top of the loop is near the counter top.