Most of the current DAZ humans, and some other figures, use morph INJection technology. Only morphs that you have INJected in to the character can be used. When you load the characters, they have "slots" reserved for the morphs, but they don't contain any actual morph instructions for changing the shape. If you have "show hidden parameters" selected in the Parameters palette option menu (the triangle button at top-right of the palette) you will see these empty morph slots, in grey, but they won't have any effect on the figure. For the most part, you need to buy the morph packs for the figure to use the sliders, though some figures (such as Michael 3) do include a few injectable morphs - look in the Pose library, in a folder named "!M3 Expressions INJ" for example.